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The Effect of Streaming Chat on Perceptions of
Debates

Victoria Asbury∗, Keng-Chi Chang†, Katherine McCabe ‡,

Broadcast political media is becoming more social. Technology has advanced

to the point where now many online video “livestreams” come with embedded live-

streaming chatboxes, uniting the on-screen and social components into one real-

time, integrated experience. We investigate how these chatboxes may shape per-

ceptions of political events. We conducted a field experiment during the Septem-

ber 2019 Democratic Primary Debate where subjects were assigned to view the

debate with or without streaming chatboxes. Subjects were encouraged to view

the debate on the ABC homepage (with no chatbox), on FiveThirtyEight.com

(expert chat) or on Facebook (social chat). We use text analysis to character-

ize the types of comments in the two chat streams. Our experimental findings

indicate that Democratic subjects assigned to the Facebook chat condition re-

ported lower affect towards Democrats and a worse viewing experience. The tone

of candidate-directed comments also matter: We find that the number of nega-

tive comments about a candidate on the social chat predicts a decreased feeling

thermometer rating of that candidate, while the number of positive comments

predicts increased belief that that candidate will improve in the polls.

∗Harvard Univeristy
†University of California San Diego
‡Rutgers University
§Penn State University
¶University of Maryland

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Media consumption is becoming a more social and interactive endeavor.
Media
producers encourage audiences to engage with their content via social media, and media
consumers take to social media as a “second screen” to see what others think as they
watch various types of content, from pre-recorded season finales to live events. More
recently, the advent of live video with integrated streaming chat is gaining in popularity
among younger generations. “Streaming chat” offers a viewing experience where the
live video and real-time commentary are embedded on a screen together, encouraging
viewers to immerse themselves in both sources at the same time.
Young politicians like Congresswoman Alexandria Ocasio-Cortez have famously
adopted livestreams with streaming chat as a powerful political tool, and increasingly,
major political events are also being broadcast through platforms that offer streaming
chat options. This technological change has the potential to modify the effect of live
broadcasts on the viewing public by changing a number of parameters of the experience
that had been constant for decades.
Specifically, previous scholars have shown that exposure to commentary about polit-
ical events (specifically, political debates) can alter perceptions of these events. The rise
of “dual” or “second screening”—where viewers follow along with social commentary
during the live broadcast—offers an enhanced source of influence in real time (Gil de
Z´u˜niga, Garcia-Perdomo and McGregor, 2015; Vaccari, Chadwick and O’Loughlin,
2015). However, despite the more recent and rapid rise in integrated streaming chat
during live political events, we have little evidence to show the potential effects of this
technological change on political attitudes and behaviors.
To examine these potential effects, during the September 2019 Democratic Primary
Debate, we pre-registered1 and conducted a digital field experiment, modeled after
the Gross, Porter and Wood (2019) panel experimental design, to study the influence
of these real-time comment sections on the public’s perceptions of the debate, the
participating candidates, and overall trust in the democratic process. In a two-wave
survey, using Amazon’s Mechanical Turk to recruit subjects, we randomly assigned and
encouraged 1095 participants to watch the debate on one of three online platforms: the
ABC News website, which provided a livestream of the debate without a streaming
chat; the ABC News Facebook page, which provided social commentary from public
Facebook users alongside the video; and the FiveThirtyEight website, which provided
live expert commentary from political analysts alongside the video. We simultaneously

1Pre-registration available at [REDACTED]

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collected the comment feeds from the social and expert conditions to characterize how a
key aspect of the treatment– the content of the chatboxes– differed between conditions.
Directly following the debate, participants completed a follow-up survey.
Because this is a field experiment, our design is high in ecological validity. Subjects
consume a prominent political media event in real time, from the comfort of their own
homes; we merely prompt them to vary the platform they use to view the debate. Our
sample consists entirely of people who were already planning to watch the debate. This
is not, of course, representative of the general population, but we believe that this non-
representativeness is epistemically desirable. Forcing media upon people who would
never choose to consume it produces potentially misleading counterfactuals (Arceneaux
and Johnson, 2013).
Even though we lack explicit control over the content of the two treatments, we are
able to trace the important dimensions of the expert and social chat contexts using
text analysis to infer the nature of one of the most critical aspects of the treatments.
Descriptively characterizing the “social” chat feed on the official Facebook livestream
of the debate is not trivial, and understanding the contours of this social chat can help
illuminate the potential effects of exposing subjects to different platforms. To this end,
we hand-coded 6,500 “social” comments for both topic and sentiment, to supplement
machine-coding methods.
Our results reveal stark differences in the real-time commentary on the “social”
Facebook and “expert” FiveThirtyEight pages. The “social” commentary was signifi-
cantly more negative in tone than the “expert” commentary and more likely to include
comments that score high on scales designed to measure online toxicity. This staid
description undersells the distasteful and sometimes extremely offensive nature of the
Facebook chat. The volume and intensity of the comments to which viewers of the
debate with the streaming chat modality were exposed has no analogue.
The results of our randomized experiment tightly match these descriptive results.
Democratic respondents who were encouraged to watch the debate on the ABC News
Facebook page came away from the debate with more negative feelings toward Democrats,
aligning with the negative depictions of the debate participants in the real-time com-
ments.
The text analysis also allows us to differentiate comments about different candidates,
enabling us to capture changes in a number of candidate-level opinions. The number of
negative comments about a given candidate is strongly predictive of decreased feeling
thermometer evaluations of that candidate in the “social” condition relative to the

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control. Notably, Vice President Joe Biden was the target of the highest number of
negative comments (the modal such comment was about his advanced age) and saw
the largest decline on the feeling thermometer scale—about 10 points, on the 100-point
scale. Senator Kamala Harris received the second most negative comments (mostly vile
misogyny) and also saw a decline on the feeling thermometer of about 10 points.
On the other hand, the number of positive comments about a candidate was highly
correlated with an increased perception that that candidate would do better in the polls
after the debate. The number one candidate on both positive comments and predicted
poll bump was Senator Bernie Sanders; number two on both dimensions was Andrew
Yang.
It is worth noting that some of these findings went against some of our initial
expectations. The development of new technologies for people to interact with others
while consuming media is undoubtedly exciting in its potential to stimulate viewers,
and we anticipated the potential for positive effects of the social chat on engagement.
However, our findings point out potential pitfalls of real-time comments. Just as the
broadcast era of political news proved to have priming and agenda setting effects on
political attitudes (Iyengar and Kinder 1987), the streaming chat era may have its own
impact in disrupting learning and information processing as citizens are exposed to the
carnivalesque thoughts of their peers online.

Bennett and Iyengar (2008) famously describe a “new era of minimal effects,” pri-
marily due to self-selection among media consumers. Streaming chat feeds are a novel
technology in the density, diversity and intensity of the media stimuli they deliver, and
they present a case where non-minimal effects can be expected.

The technological capacity for audiences to engage in mass communication on one
screen while consuming broadcast media on another (most often a “media event” that
coordinates the interest of a large group of people (Dayan and Katz, 1992)) has existed
for over a decade, and while earlier studies documented the existence and prevalence
of the phenomenon Jungherr (2014); Larsson and Moe (2012), theoretical interest in
dual or double screening began in earnest with Gil de Z´u˜niga, Garcia-Perdomo and
McGregor (2015) and Vaccari, Chadwick and O’Loughlin (2015).
“Dual screening” or “second screening,” where viewers of political television media

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participate in real-time conversations in online platforms like Twitter, has been shown
to the change the effect of media consumption on attitudes (Barnidge, Gil de Z´u˜niga
and Diehl, 2017; Gil de Z´u˜niga, Garcia-Perdomo and McGregor, 2015; McGregor and
Mour˜ao, 2017; Vaccari, Chadwick and O’Loughlin, 2015).
Traditionally in political
science, the news media are thought to have the power to set the agenda and change
the criteria by which we, as consumers, evaluate political figures and form attitudes
on political issues (Iyengar and Kinder, 1987). The addition of a second screen could,
at minimum, muddle the effects of media on public opinion. However, the extent to
which this occurs depends on the amount of attention consumers give to the “second
screen” and whether they treat online commentary similar to actual news content in
deciding whether to “accept” the information in the commentary as considerations that
can influence their beliefs (Zaller, 1992).
Our study focuses on an innovation to dual-screening. In recent years, streaming
chatboxes alongside a related video feed, all on one screen, have become increasingly
popular.
Already the norm in livestreams of sports and video game competitions,
chatboxes have recently been added to online streams of political media. In many ways
“integrated real-time streaming chat” (hereafter referred to as just “streaming chat”)
amplifies the potential effects of the second screen. Viewers are now immersed in both
the video livestream and the real-time comments during the viewing experience.
The question, therefore, remains: Do real-time comments have the power to shape
what is salient and accessible as consumers–potential voters–form their attitudes on
political figures and events? And does it have the power, in turn, to change people’s
attitudes?
We propose three theoretical pathways by which the addition of streaming chat
windows to broadcast media might affect perceptions of the media event: frequency,
content, and context of the comments that stream. Our discussion is premised on a
technosocial context similar to the Facebook chat in our study, but we hope that identi-
fying theoretically distinct pathways will extend the temporal validity of our theory and
results in what is likely to be a rapidly evolving communication technology (Munger,
2019).

• Frequency: A high volume of streaming comments increases the potential for
distraction and information overload.

• Content: Discussion of issues serves as a prime, increasing their salience. The

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nature of the messages as a discussion network increases the likelihood of persua-
sion.

• Context: The composition of the commenters is not obvious to the viewer, which
will lead them to over-estimate the quality of the information source for making
inferences about public opinion.

We will now trace the theoretical antecedents of each of these pathways and hy-
pothesize their potential consequences within the context of the setting of our study:
the September 2019 Democratic Debate. As we explain in more detail below, our two
treatment conditions involve assigning subjects to view two different types of stream-
ing chat—on Facebook (social condition) and on FiveThirtyEight (expert condition)—
which vary each of these parameters, producing different predictions. “Expert chat” is
a much less prominent phenomenon than streaming social chat, and less novel, so while
we consider social chat our primary treatment condition of interest, the expert chat
prediction serves as a useful check on the mechanisms driving the effects we observe for
streaming chat.

The Setting: The September Democratic Debate

Debates are an exemplar of the kind of political “media event” for which streaming
chat is relevant, but they are also political media events in their own right. Primary
presidential debates are crucial vehicles for disseminating information and setting cam-
paign agendas. Indeed, studies have found primary debates can influence perceptions
of candidate viability and electablity (Yawn et. al 1998), affect towards candidates
and issue salience (Best and Hubbard 1999), knowledge of candidates’ policy positions
(Benoit et. al 2002), and voter preference (Benoit et. al 2010). Thus, primary debates,
particularly those early in the primary season, are crucial political events, as they are
mechanisms for introducing candidates to the voters, many of whom are not decided
on a given candidate.
In the past, newspaper journalists were the chief political actors that signaled to
readers what information in a presidential debate mattered after the debate ended
(Benoit 2017).
As cable news became an increasingly important domain for politi-
cal analyses, cable news hosts and commentators also became important agents who
communicate to audience members how debate performances should be interpreted

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(Fridkin et. al 2008). The rise of dual-screening, however, has the potential to break
down journalistic gate-keeping and influence perceptions in real-time.
The September 12, 2019 Democratic primary debate hosted by ABC News and
Univision was a major media event. The September debate was the third debate of the
2020 presidential election season, however, it was the first time all of the top-polling
Democratic candidates would be on one stage and able to confront each other directly.
An ABC News press release after the night of the debate noted: “ABC News Democratic
Debate coverage drew 2.9 million unique visitors and 11 million video views (ABC News
Live and VOD) across ABC News digital properties and distributed partners including
Facebook Live, Twitter, Apple News, YouTube, Hulu and Hotstar.” Given the amount
of interest in the third primary debate and the high level of live-streaming and digital
engagement the event attracted, the presidential debate featured in this study serves as
an appropriate context for exploring the effect of streaming chat on political attitudes.

Frequency: Distraction and Affective Processing

Some early research on second screening focused on the capacity of the second screen to
distract the audience’s attention (Gottfried et al., 2017; Van Cauwenberge, Schaap and
Van Roy, 2014; Van Cauwenberge, dHaenens and Beentjes, 2015). However, research
that centers the purposiveness of the act of second screening emphasizes the agency of
the viewers in selecting when and where to consult the second screen (McGregor and
Mour˜ao, 2017), and whether to actually participate by posting commentary (Vaccari,
Chadwick and O’Loughlin, 2015). For example, in order to follow a hashtag on Twitter,
someone has to actively open Twitter and search for relevant comments – an act that
is inherently purposive. Further, Gil de Z´u˜niga, Garcia-Perdomo and McGregor (2015)
determines the type of person who is actually likely to engage in second screening,
thus establishing the extent of these effects. This is particularly important because
dual-screening requires viewers to actively engage with a second source of information.
If they were merely watching the broadcast, incidental exposure to the second screen
would be impossible.2

Consuming media with streaming chat is less likely to be purposive as more media
sources embed chats with their video streams, forcing scholars to reconsider findings

2Another possibility is that users of a given chat platform (here, Twitter) become incidentally
exposed to the discussion of the media event and either gain some information about it or even decide
to tune in. Integrated streaming chat renders this process irrelevant.

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about second screening which center the purposiveness of the act.
This shift also
increases the range of people exposed to streaming chat; as Gil de Z´u˜niga, Ard`evol-
Abreu and Casero-Ripoll´es (2019) demonstrate in the case of another novel political
communication technology (WhatsApp chat among extended family groups).
Even more significantly, the unity of the broadcast and the stream in the visual
field makes streaming chat theoretically distinct from second screening. The richness of
the visual information provided on a single screen showing a broadcast combined with
streaming chat is unparalleled. Streaming chat is often located at the same eye level as
the video broadcast, so the viewer consumes both automatically. This undercuts the
purposiveness that even moving the eye between two screens provides, increasing the
relevance of concerns about distraction. Just by tuning into a livestream with streaming
chat, even if a viewer intends to focus on the video, it is likely they may be incidentally
exposed to the real-time comments. In contrast, dual-screeners watching a broadcast
and also tracking a given hashtag on Twitter that refers to the media event being
broadcast must click into the Twitter interface, scroll down, and then click at the top
to load the most recent tweets. The experience of second screening is thus intrinsically
more purposive than is observing the streaming chat flow across the screen.
We hypothesize that this element of the streaming chat platform design will change
how viewers experience the media event relative to contexts where viewers can focus
exclusively on the video:

• Hypothesis 1: Increased distraction from the streaming chat will cause viewers
to consider the debate less enjoyable and informative, but the increased number
of stimuli will cause them to be more engaged.

The expert chat has a dramatically lower frequency of comments, decreasing the
problem of distraction. The addition of a small number of considered and informed
comments, we predicted, would only enhance the process.

• Hypothesis 1(e): Increased commentary from the expert chat will cause viewers
to consider the debate more enjoyable, informative and engaging.

Recent research on the experience of consuming political media in the contemporary
context of total saturation and extreme affect can cause people to feel overwhelmed,
anxious and angry (Wagner and Boczkowski, 2019). There is a wealth of evidence for the

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important role these emotions play in political communication and participation (see
Wagner and Morisi (2019) for a recent summary), so we also test whether streaming
chat causes viewers to experience these negative emotions.

• Hypothesis 2: Streaming chat will cause viewers to be more angry and anxious.

The expert chat does not threaten to overwhelm the viewer, instead promoting a
measured and reasoned response to the broadcast.

• Hypothesis 2(e): The expert chat will cause viewers to be less angry and anx-
ious.

Two of the processes most central to contemporary theories of political communica-
tion are framing and priming. Cacciatore, Scheufele and Iyengar (2016) argue that the
two are often confused, and we follow the conceptual distinction they draw to evaluate
priming effects in our study. Priming changes the relative salience of different character-
istics or issues in determining how viewers evaluate politicians.3 Theoretically grounded
in the cognitive process of “spreading activation,” priming affects which thoughts are
immediately subsequent to considering a given politician (Iyengar, 1987).
The concept was developed for the era of broadcast media, and within the debate
setting, originally concerned commentary immediately before or after a debate broad-
cast, given the temporally linear nature of the medium.
Second screening enables
near-instantaneous priming, as the viewer can consume commentary on a given debate
response while it is still ongoing. Past work has shown that second screening increases
the likelihood of persuasion among consumers of broadcast media (Barnidge, Gil de
Z´u˜niga and Diehl, 2017), likely due to the immediacy of audience feedback.4

Furthermore, the primes produced in unmoderated streaming chat potentially in-
clude primes that would not be produced by traditional media sources. This includes
primes that are openly racist, sexist or otherwise discriminatory, and primes that are
simply untrue or, bluntly, completely asinine.5
In a related context, Anspach and

3It is possible that these effects may represent learning new, salient information about candidates
in addition to increasing the salience of topics that voters may already be familiar with about the
candidates.
4Previous research has also found that engagement in contentious political discussions on social
media increases political persuasion (Gil de Z´u˜niga, Barnidge and Diehl, 2018).
5In hand-coding all of the comments in our streaming chat sample, our favorite example was “WHAT
IS CORY BOOKER’S REAL NAME????? what is he hiding”.

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Carlson (2018) find that social commentary on news posts shared on platforms like
Facebook is both misleading yet consequential. Holding the content of a news story’s
summary constant, the addition of social commentary that misrepresents that summary
can cause people to recall incorrect information rather than that contained in the story.
The social information is more salient.
In many cases, the topics or “primes” present in the debate comments are bad for
the democratic process, encouraging voters to evaluate candidates on criteria that are
unrelated to their performance and which reinforce existing inequalities. Consider the
example of Biden’s acuity. During the debate in this study, Julian Castro specifically
criticized Biden’s age, and many comments in the streaming chat mentioned Biden’s
health or acuity at various points when Biden was talking. This immediacy could sup-
plant whatever policy position Biden was attempting to link himself to, instead priming
concern about his fitness for office. Particularly in a primary election, unlike the de-
bate stage, the debate comment section may include detractors from the opposing party
who discuss topics that represent negative primes that will be used by the opposing
party in the general election, but which may be considered too damaging to employ by
copartisans in the primary.
On this pathway, the streaming social and expert chats are substantively similar in
terms of theoretical predictions. Our first hypothesis for priming effects is straightfor-
ward: that the candidates mentioned most often in the streaming chat will be salient
in the minds of viewers, and therefore, experience an increase in name recognition and
familiarity. The second hypothesis could not be fully specified in advance, and was not
pre-registered. We anticipate that the frequency and valence of particular candidate-
specific topics will influence their candidate evaluations. Empirically, we focus on the
social chat. We anticipate that the presence of detractors on social chat will uniquely
increase the quantity of prominent negative primes about the candidates, and we hy-
pothesize that this will lead to a decrease in evaluations of the candidates who are the
focus of these negative comments.

• Hypothesis 3: Candidates mentioned most often in the streaming chat will see
an increase in name recognition.

• Hypothesis 4: Viewers of the streaming chat will reduce their evaluation of
candidates in the presence of a prominent negative prime.

• Hypothesis 3(e): Candidates mentioned most often in the expert chat will see

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• Hypothesis 4(e): Viewers of the expert chat will reduce their evaluation of can-
didates in the presence of a prominent negative prime.

Our last set of hypotheses stem from two premises. First, streaming social chats are
more likely to be composed of low-quality, toxic comments than other forms of media
due to the quasi-anonymity of comments. Second, the public may incorrectly project
from these comments what the broader public thinks about a livestreamed event. Below
we explain both of these claims to derive our hypotheses.
One key feature of the social feeds coordinated using hashtags on Twitter that
are standard in the dual screening literature is that the streams are semi-permanent,
and each account that comprises the stream conveys significant social information in
its profile.
In contrast, the stream in the embedded Facebook chat is made quasi-
anonymous by the speed at which it flows; many other streaming chats are completely
anonymous. In the first block of the debate, for example, we estimate there were 60.3
comments per minute. While viewers might begin to notice frequent commenters, there
were too many for long-term reputational costs to obtain.
This quasi-anonymity has significant implications for the types of people who com-
prise the streaming chat and for the types of messages they send.
For instance, anonymity increases ”flaming” or personal attacks in online commu-
nities (Mungeam and Crandall, 2011), and removing anonymity can elevate the level
of civility in discourse in online newspaper comments sections (Santana, 2014). The
presence of anonymity also moderates the capacity for norm enforcement online; for
moderate norms like that against political incivility, anonymity decreases the effective-
ness of norm enforcement (Munger, 2017).
The presence of high levels of toxicity in a chat room can produce a positive feedback
loop, as people with a low tolerance for toxicity opt out of sending messages (Theocharis
et al., 2016). Furthermore, joining an online community where toxic language is normal-
ized causes people to comment in a more toxic manner Cheng et al. (2017). As a result
(and as we demonstrate empirically below), streaming chats are likely to be highly
toxic.
This toxic partisan incivility provides an explanation for how cross-partisan
communication can actually increase affective polarization.

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Far from the ideal conditions under which the contact hypothesis predicts will de-
crease intergroup hostility, watching toxic streaming chats entails spending time with
the cruelest, most aggressive and least thoughtful group of your partisan opponents.
Although these commenters are likely a radically non-representative sample, the con-
ditions of streaming chat obscure this fact. The presence of incivility in online political
conversations has been shown to increase affective polarization (Suhay, Bello-Pardo and
Maurer, 2018), and the current context further increases the likelihood that subjects
will update their opinion of their fellow citizens.6

Barnidge, Gil de Z´u˜niga and Diehl (2017) demonstrate the importance of second
screening by showing how it can enhance persuasion among viewers of political content.
Theoretically, this occurs because the second screen provides “social cues...[which] pro-
vide direct evidence of social opinion, which people take to be representative of public
opinion, even if they are not” (p313). This last claim references Lerman, Yan and Wu
(2016), who demonstrate the existence of the “majority illusion” that can be produced
by social networks.
Although communication scholars tend to rely on psychological processes to explain
the effects of new media technologies on beliefs, logic like that demonstrated in Ler-
man, Yan and Wu (2016) makes predictions that are observationally equivalent using a
rational actor framework. Economists have recently been developing theories of “corre-
lational neglect” that describe the fact that people tend to underestimate the amount
of correlation between different sources of information they encounter, particularly on
social media.
Social media is much “denser” than either traditional media or socialization; the
consumer is able to observe a large number of signals in a very short period of time. The
issue is that our intuitions about the informational content of each signal are misleading
because the signals are highly correlated with one another. Although this effect should
not change the direction in which a social media updates her beliefs about the world,
it does tend to magnify any belief updating, resulting in what Ortoleva and Snowberg
(2015) describe as overconfidence, which in turn causes ideological extremeness.
In the aggregate, however, this may not be normatively undesirable; (Levy and
Razin, 2015) describe the conditions under which an electorate with “correlationally
neglectful” voters can actually make better decisions.
Voters generally tend to un-

6This theory comports with survey evidence from Pew, in which “64% say their online encounters
with people on the opposite side of the political spectrum leave them feeling as if they have even less
in common than they thought” (Duggan and Smith, 2016).

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dervalue novel information relative to their longstanding beliefs about the world (see,
for example, the persistence of partisanship), and correlation neglect cuts the other
direction.

Enke and Zimmermann (2017) provide experimental evidence for the theoretical
model developed in (Levy and Razin, 2015), and demonstrate that the primary cause
behind correlational neglect is that calculating correlations is cognitively taxing. Sub-
jects with lower scores on cognitive tests exhibit higher correlational neglect, which
cannot be reduced by tripling the rewards for accuracy. Experimentally increasing the
complexity of the task increases correlational neglect.
This combination of low-quality comments and a context that encourages viewers
to make inferences about public opinion as a whole produces three sets of hypotheses:

• Hypothesis 5: Streaming chat will cause a decrease in trust in the process of
debates and democracy.

• Hypothesis 6: Streaming chat will cause an increase in affective polarization.

• Hypothesis 7: Respondents will change their estimate of the success of each
candidate in future polls based on the sentiment directed at that candidate in the
streaming chat.

The context parameters do vary significantly between the two chat conditions. The
expert chat is civil and reasoned (bordering on wonk-y), evincing a deep enthusiasm for
the process of debates and democracy. Furthermore, the expert chat clearly represents
itself as such, and should thus not cause viewers to change their opinion of others’
opinions about the candidates.

• Hypothesis 5(e): Expert chat will cause an increase in trust in the process of
debates and democracy.

• Hypothesis 6(e): Expert chat will cause a decrease in affective polarization.

• Hypothesis 7(e): Respondents will not change their estimate of the success of
each candidate in future polls based on the sentiment directed at that candidate
in the expert chat.

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To examine the effects of media platforms on political attitudes, we conducted a digital
field experiment using Amazon Mechanical Turk (MTurk) to recruit participants. Re-
cruitment took place in two parts. During Wave 1, a Human Intelligence Task (HIT)
was made available to all MTurk workers residing in the US with an approval rating of
95 percent or higher. Wave 1 included 2352 respondents. Respondents who specified
that they were likely to watch the debate, had a Facebook account, and could watch
the debate on a computer were deemed eligible and invited to participate in a second
survey after the debate 7

A total of 1315 respondents were qualified for participating in the second survey,
and 1095 of these respondents indicated an interest to participate. Our sample includes
only people who are interested and likely to watch political debates and able to watch
these debates online, which means our treatment effects are estimated on a sample that
reflects a population that might plausibly be “treated” in this manner during similar
events in the real world, an advantage for external validity.

Experimental conditions: ABC, Facebook and FiveThirtyEight

Our experiment is an encouragement design with three conditions. The design is mod-
eled after Gross, Porter and Wood (2019) who investigate the effect of viewing political
debates on different broadcast networks by using an online field experiment to ran-
domize the channel where subjects viewed the debate. In our study, respondents who
indicated that they were interested in participating in the second survey were randomly
assigned and asked to watch the debate on one of the following livestream platforms:
FiveThirtyEight (Expert condition, N=243 Democrats; N=364 all), ABC News Face-
book page (Social Media condition, N= 263 Democrats, N=365 all), or ABC News
(Control condition, N= 264 Democrats, N=366 all). Respondents were given links to
these websites at the end of the Wave 1 survey and were also sent a reminder email
prior to the debate with a direct link to the livestream. For screenshots of three debate
platforms, see Figure 10 in the Appendix. At the end of the debate, a link to the follow-
up survey was emailed to each respondent who indicated an interest in participating in
Wave 2.

7Eligible respondents were offered a bonus payment of $1.50 and an entry into a $100 raffle for their
participation in the second survey

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During the Wave 2 survey, respondents were asked questions about their reactions
to the debate, their emotional state, predictions regarding polls, familiarity with the
candidates, trust in the government, and political polarization. Respondents also rated
their feelings towards the two major political parties and the Democratic presidential
candidates during a series of questions using feeling thermometers. After answering
the survey questions, respondents provided responses to detailed compliance checks,
provided open-ended responses noting what stood out about each candidate, and were
then re-asked their party identification. (See online appendix for question wording.)
The Wave 2 respondents are generally balanced across assignment conditions: N=305
in the ABC Control condition (84% recontact rate), N= 298 in the FiveThirtyEight Ex-
pert condition (82% recontact rate), and N=305 (84% recontact rate) in the Facebook
Social Media condition. Our sample includes 648 Democratic respondents who com-
pleted Wave 2,8 and 576 Democratic respondents who completed Wave 2 and reported
watching at least part of the debate.
Our primary analyses will be limited to this subsample of Democrats who watched
at least part of the debate, as many of the questions in our follow-up survey specifically
ask about reactions to the debate, for which respondents can only answer if they did
watch. We focus on Democrats, as they comprise the substantial majority of the sample,
and we anticipated potential heterogeneous effects by partisanship.9 The table below
summarizes the number of respondents in each condition assigned during Wave 1, as
well as respondents who will comprise the analysis sample of Democrats who watched
at least part of the debate.
As with most encouragement designs, treatment assignment does not equate to the
receipt of treatment. Our study has two-sided noncompliance (Gerber and Green, 2012)
where some subjects in the Control condition who watched the debate may have been
“treated” by viewing social or expert commentary, and some subjects in the treatment
conditions who watched the debate may have opted not to view the debate on the
assigned platform (going untreated).10 We conduct supplemental analyses that account

8This subsample includes similar recontact rates across conditions: control (N=224, 84.8% recontact
rate), social (N=221, 83.5% recontact rate), and expert condition (N=182, 84.0% recontact).
9Supplemental results for Republicans are in the appendix.
10At the end of the Wave 2 survey, we asked how and on what platform respondents watched
the debate. About 70% of respondents (73% of Democrats) self-reported watching at least part of
the debate and watching the debate on the platform where they were assigned. Self-reported rates
of watching the debate on the assigned platform was somewhat higher in the control (74% overall,
75% among Democrats) and social (75% overall, 77% among Democrats) conditions than the expert
condition (62% overall, 66% among Democrats). We believe the lower propensity for respondents to

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for compliance in the results section. Additional details on compliance and balance
across experimental conditions are in the appendix.

Full Sample
Control
Expert
Social
Total N

Assigned
366
364
365
1095
Participated in Wave 2
305
298
305
908
Participated in Wave 2 and Watched Debate
279
254
276
809

Democrats Only (including leaners)
Control
Expert
Social
Total N

Assigned
264
243
263
770
Participated in Wave 2
224
203
221
648
Participated in Wave 2 and Watched Debate
204
174
198
576

Analysis of Expert and Social Media Comments

Our results first examine the content of the streaming chats on the ABC News Facebook
page or FiveThirtyEight. We performed a series of computational text analyses of the
comments found in each stream and a hand-coding of the Facebook stream for subject,
tone and topic.
Our text analyses are organized to focus on the three theoretical
mechanisms through which we believe chat streams may influence perceptions of the
debate and the candidates: frequency of the chat, topics discussed that may prime
viewers, and the context or tone of the commentary.
To perform the analysis, we scraped the comments from each of the streaming chats.
For the FiveThirtyEight chatbox, we were able to extract all the comments made by
experts during the debate. For Facebook, we first manually expanded the chatbox,
then we extracted the comments from the available HTML file. We were not able to
extract all the comments in the chatbox, but a large sample of the comments which
Facebook makes available through our manual search. In addition, we did not collect
replies to the comments and reactions from the users. The Facebook streaming chat
started before and continued after the debate. We decided to analyze comments made
during the three-hour debate broadcast windows, since we asked our respondents to
watch only the debate.

watch the debate and watch the debate on the FiveThirtyEight website, when assigned, may be due
to the quality of the viewing platform for the debate. See appendix for details.

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In the expert chat, we collected 314 comments with 23,437 words in total, and 74.6
words on average by comment. On Facebook, we have a sample of 6,915 comments
with 53,092 words and an average of 7.75 words by comment.
Overall, comments in the social condition are more frequent and considerably shorter
compared to the expert chat. Assuming our sample represents most of the comments
a user would be exposed to during the time of the debate, based on our sample, users
observed 1.68 comments per minute in the expert chat and 38 comments per minute
in the social chat. The difference in frequency makes sense with our theory of a more
chaotic environment on the social condition chatbox compared to the expert chat.
Figure 1 presents the evolution of the comments by minute on both conditions. The
figures clearly depicts the high frequency of comments on the social condition, and the
concentration of them in the first hour of the debate. On the other side, the expert chat
is less intense and more evenly distributed across the four hours of debate. In the first
block of the debate, for example, there were 60.3 comments per minute on Facebook,
and only 2.3 on the expert chatbox.

Figure 1: Distribution of the Comments by minute during the Debate

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In this second section, we assess how participants are communicating on the chat
streams, looking at various dimensions of toxicity.
These aggregate measures may
influence overall levels of trust in the democratic process and levels of polarization.
We use Google’s Perspective API, a content moderating tool that is the industry
standard for automatic detection of toxic content in written comments. 11 We present
the results considering the levels of toxicity using the score created by the model clas-
sifying the comments.
Figure 2 presents the proportion for the toxicity scores in four dimensions - toxicity,
severe toxicity, threat and insult. We calculate the proportion classifying as “1” all the
comments which surpass the score of 0.5 in each dimension. The differences between the
social media and expert chat are stark – levels of toxicity in all the four dimensions are
undetectable in the expert chat, while more than 15% of the comments on Facebook are
considered toxic. Overall, the Facebook chat exhibits high levels of negative comments,
with insults and toxic comments appearing often during the debate. (See Appendix for
the full distribution of toxicity scores by condition.)

Our theory expects priming effects from particular characteristics or issues raised on the
chatboxes during the debate. Our findings so far indicate that toxicity and negative tone
is predominant on the Facebook chatbox compared to the expert condition. However,
our automated methods do not reveal which issues or characteristics of the candidates
were more salient for the users talking about the debate. Therefore, with the purpose of
identifying these issues, we hand-coded 6,500 comments in the social condition.12 In our
hand-coding, we focus on the Facebook comments because our goal is to disentangle
the priming effects, in particular negative priming, among the social and the expert

11Perspective uses a convolutional neural net model to score the toxicity of an input text. Toxic is
defined as a rude, disrespectful, or unreasonable comment that is likely to make one leave a discussion.
The model was built using millions of comments from the internet, using human-coders to rate the
comments on a scale from very toxic to very healthy, and using this large data as training information
for the machine learning algorithm. We uploaded the content of the comments in each treatment
condition.
12We hand-code comments during approximately the first 2.5 hours of the debate. We stop coding
during a moment when protesters disrupted the debate, and many comments started describing the
debate as ”over.” This decision focuses our coding on the substantial majority of comments that were
made during the active debate.

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condition, and allowing a better understanding of the experimental results.
First, we read all the comments on the Facebook streaming chat with the purpose
of classifying when a comment was directed at one of the candidates in the debate.13

We considered a comment as being directed to the candidates when the text explicitly
mentioned the candidates, or implicitly making a reference to some policy, character-
istics, or political stand of the candidate. Three coders hand-coded all the comments,
and, to avoid false positives, we included only comments classified as being about the
candidates by at least two out of the three coders We end with a sample of 1,889 com-
ments. Two additional coders read through all the selected comments, and classified
the content according to the topics discussed and sentiment or polarity (whether a
comment was negative, neutral or positive about the candidate.
Figure 3 presents our results. On the left is the the total number of comments about
each candidate in the Facebook streaming chat, and the overall polarity associated.
Overall, Biden and Sanders received most of the attention followed by Harris and Yang.
The strong presence of Yang is surprising considering he was not one of the front-runners
of the primaries; he was, however, widely considered the “candidate of the internet,”
and his Universal Basic Income proposal generated a lot of attention.
For most of

13Supplemental analyses in the appendix use automated dictionary-based methods for describing
the frequency of candidate mentions and the sentiment of comments.

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the candidates, the comments are mostly negative, with special attention to Harris
and Biden, with 85% and 75% of negative comments out of their total share.
On
the other side, Sanders, Yang, Buttigieg and Klobuchar are the only candidates who
received proportionally more positive comments, though Klobuchar received very few
comments, overall.

Figure 3: Comment Polarity by Candidate, Facebook Streaming Chat

To understand which issues are being primed in the streaming chat, Figure 4 displays
the results of our hand-coding of the comments. We read each comment and classified
the subject of the comment. Comments were allowed to be about multiple topics, and if
a comment was unclear or its meaning ambiguous, it was left uncoded.14 This analysis
gives a much richer understanding of the content of the comment. Because most of the
comments are negative, this, in part, means categorizing the types of insults directed
at the candidates.
Overall, there was a remarkable degree of consistency in these attacks—so much
so that several commenters accused commenters of being Russian trolls.
We were

14Appendix Table 4 presents a more detailed analysis of the words that define these hand-labeled
topics. We also omit from this analysis comments that were generically negative or positive, such as
“Yang 2020.”

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unfortunately unable to collect any information about these commenters, but there
were clearly some copy-pasted textual “memes” repeated throughout the debate. We
think it is entirely possible that a significant number of the comments were produced
by a small number of trolls foreign or domestic. This is not a limitation of the current
study: this is a realistic feature of open Internet platforms in 2020.

Figure 4: Top Three Topics for each Candidate

Biden was the most frequently mentioned candidate, and the top three topics were
all extremely critical: mocking his age (topic labeled AgeTooOld); accusing him of
being creepy or handsy (topic labeled “SexualPredator”); and suggesting that he was
physically unwell. Sanders was also mocked for being old, and was often described as
a socialist or too far to the left.
These criticisms were harsh, and while they had generally been avoided during
the Democratic primary, in that these criticims were not brought up by their debate
opponents15 they may not be considered outside the bounds of legitimate democratic
deliberation. The comments directed at Harris, however, were generally beyond the
pale. The most common comment accused her of “sleeping her way to the top,” in

15The exception happened during this debate: Castro intimated that Biden was too old to be
running, which generated the vast majority of comments about Castro during this debate.

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sometimes graphic terms. Many others made fun of her affect (e.g., suggesting she was
“drunk”), and/or were straightforwardly misogynistic.
Other notable topics include praise for Yang’s UBI proposal and Buttigieg’s polished
and well-researched plans.
There were several mentions of O’Rourke’s strong anti-
gun statement and Booker’s history as mayor of Newark. The most common single-
candidate topic, however, was mockery of Warren by reference to her having claimed
Native American heritage. Many of the comments in this category were simply echoes
of Trump’s “Pocahontas” moniker.

We now turn to our survey experimental results. We present results for Democratic
respondents (including those who lean toward the Democratic Party when forced to
choose between the Democratic and Republican Party) who completed the Wave 2
survey indicated watching at least part of the debate (N=576).
In each analysis, we present two types of average effects: First, we report the av-
erage marginal effect of assignment to the Expert condition, relative to the Control
condition, and assignment to the Social condition, relative to the Control. These are
calculated using linear regressions of each outcome on the treatment assignment indi-
cators. The figures to follow present the coefficient point estimate, as well as 90% and
95% confidence intervals.
In addition, we report one type of complier average causal effect (CACE) using
instrumental variables (IV) regression. To do so, we consider the two pairwise compar-
isons of Expert vs. Control and Social vs. Control, separately. We code each respondent
in the analysis as being simply “treated” or “untreated” for each comparison based on
whether or not they reported watching the debate on the assigned platform.
For each comparison, we conduct a two-stage least squares regression where treat-
ment assignment is used as an instrument for whether the respondent actually received
the treatment (Gerber and Green, 2012). We find compliance rates of 75% for the Ex-
pert condition and 81% for the Social condition by this method.16 We report the point
estimate of the CACE and 90% and 95% confidence intervals for this analysis in the

16This is calculated within the sample of Democrats who watched at least part of the debate.
Compliance is based on the first stage regression where treatment receipt is regressed on treatment
assignment. The CACE is the ratio of the coefficient for the effect of treatment assignment on each
outcome over the compliance rate.

Scene 23

figures. We interpret these effects as local– the effect only among those who complied
and watched the debate on the assigned platform because they were assigned to do so.17

Testing Hypotheses Related to Frequency Effects

Our first set of hypotheses discussed how participants would rate their overall debate
experience. In particular, we hypothesized that streaming social chat may lead viewers
to find the debate less enjoyable and informative, though potentially more engaging due
to the increase in stimuli. In addition, we hypothesized that the comments in social chat
may also increase the extent to which viewers experienced negative emotions during the
debate–specifically, anger and anxiety. We generally anticipated the opposite effects for
the experience of the expert chat.
Figure 5 displays the results. Overall respondents assigned to the Social condition
had more negative experiences with the debate than respondents assigned to the Control
condition. As expected, respondents who were assigned to watch the debate on the
Facebook platform found the debate both less informative (n.s.) and less enjoyable
(p < 0.05) on average. Contrary to our expectations, respondents assigned to the Social
condition also found the debate less engaging (p < 0.05). After adjusting our results
for multiple comparisons based on the five outcomes, the p-values for how enjoyable
and engaging the debate is move above conventional levels of statistical significance.
Respondents in the Social condition also reported slightly, but not significantly, higher
rates of feeling angry and anxious from watching the debate. Thus, at minimum, the
results show that the encouragement to watch the debate on Facebook, did not lead
debate watchers to have a more satisfying experience. Instead, we have some support
that exposure to social media comments can lead to both a less informative and overall
negative experience.
In addition, contrary to our expectations, assignment to the Expert condition did
not have opposing effects to the Social condition. Respondents in the Expert condition
generally expressed similar, though often slightly more muted, reactions to those in
the Social condition. In almost every case, the effects (relative to the Control) were
indistinguishable from zero. The one exception is that respondents in the Expert condi-
tion found the debate significantly less engaging.18 In this case, the increase in stimuli

17Note: Our design may include ”always-takers” and ”never-takers” who do not adjust their viewing
behavior based on their treatment assignment. We assume no defiers.
18This result remains significant at the p < 0.10 level after adjusting for multiple testing of the five
outcomes.

Scene 24

served only to turn people off of the debate.

Testing Hypotheses Related to Content Effects

Our second set of hypotheses anticipates that there will be a connection between the
focus of the comments and the extent to which respondents report they are now familiar
with the candidates after the debate. The results are displayed in Appendix Figure 11.
Overall, we see little movement in either the Social or Expert conditions relative to
respondents assigned to watch the debate on the ABC News Website. We suspect that
this may be because the focus of the comments in the chat streams often tracked with
the amount of speaking time each candidate had and pre-existing poll performance.
We also hypothesize that candidate-specific favorability may be influenced by the
degree to which candidates were discussed in negative ways in the commentary. To
assess this, we examine feeling thermometer ratings toward each of the candidates
(Figure 6).
As shown in Figure 6, we find that respondents in the Social condition came away
with more negative perceptions of all debate participants, on average (bottom right),
relative to the Control condition.19

19Figure 12 plots the average feeling thermometers for each candidate by condition. Overall, Sanders
and Warren had the warmest average ratings, while Klobuchar had the least warm ratings. However,

Scene 25

Comparing across conditions, respondents assigned to watch the debate on the ABC
News Facebook page came away with more negative feelings toward Biden, Harris, and
Booker. These results remain significant (p < 0.05) when adjusting for ten candidate
outcomes. Respondents also become more negative in their feelings toward O’Rourke
and Castro, though these results move above conventional levels of significance after
adjusting for multiple testing.
Results for the Expert condition are generally more
muted, except in the case of evaluations of Castro, which are significantly more negative
in the Expert condition.

candidates generally received neutral to positive ratings. No Democratic debate candidate was viewed
extremely coldly, on average.

Scene 26

These candidates, in particular Biden, Harris, Booker and O’Rourke, are among
those who received proportionally more negative comments in our text analysis of the
social streaming chat. To provide a intuitive visualization of this pattern, Figure 7 plots
the average difference in the feeling thermometer between the social and the control
condition for each candidate on the sum of comments we labelled as negative on the
Facebook streaming chat.

Figure 7: Negative Comments Decrease Candidate Feeling Thermometers

Klobuchar
Cast ro
Butti ie
.10
Sanders
Warren
O'ßourke
Booker
Biden
Harris

Testing Hypotheses Related to Context Effects

A final set of hypotheses assessed the extent to which respondents would infer from
the commentary how the general public views the candidates. To test this, we assess
whether respondents think that the candidate will do better in the polls as a result of
the debate (Figure 13).
Across all conditions, respondents indicated that some candidates were more likely
to perform better in the polls after the debate than other candidates. Figure 8 plots
the proportion of respondents who indicated a candidate would likely do better in the

Scene 27

polls the following week by condition. We notice some variation by condition, though
the variation between conditions is often smaller than the variation between candidates.
Respondents in each condition pointed to Warren and Sanders as the better-performing
candidates, while respondents were less likely to indicate that front-runner (at the time)
Biden would do better in the polls after his debate performance.

Figure 8: Candidate Poll Performance Averages

Do pous
III
social
social
PmpMtim WA 00
WI" 00 in Pons
Sco
Sco
castm WW Do
Yang Do pous
social
social
sanders Do Better in pous
social
00
Sco
social

Respondents in the social condition were less likely to predict Booker or O’Rourke
would perform well in the polls, as we indicate on figure 8, and respondents in the
social condition were more likely to predict that Yang and Sanders would do better

Scene 28

in the election polls after the debate.
Notably, Yang and Sanders were candidates
who received relatively more positive comments on the ABC News Facebook stream
compared to other candidates. Figure 9 displays the correlation between the number of
positive comments a candidate received in the social chat and the difference in projected
poll performance between the social and control conditions.

Figure 9: Positive Comments Increase Expected Poll Performance

In addition, we hypothesized that viewing the debate with social chat may lead
respondents to become more polarized, and decrease their trust in the political process.
Similar to the first set of hypotheses, we do not have shared expectations for the Expert
chat. Instead, we anticipated that viewing expert analysis may help to increase trust
and reduce polarization. Figure 14 (Appendix) displays feeling thermometer ratings
toward the Democratic Party, Republican Party, and a measure of affective polarization
(the difference between these two ratings). Respondents in the treatment conditions
tended to come away from the debate with slightly, but not significantly, more negative
ratings of the Democratic Party (in contrast to their more negative feelings about many
Democratic debate participants). We find null results for treatment effects on ratings

Scene 29

of the Republican Party of affective polarization.
Similarly, despite our expectations, we find no significant effects of assignment to
the treatment conditions on perceptions of trust in political parties, the wisdom of the
public in making political decisions, the desire to want political officials to work with
those with whom they may disagree, or perceptions of the role of the debates as part
of the democratic process (Figure 15, in the Appendix).

Does streaming chat alter viewer perceptions of political debates? We first demonstrate
that real-time social commentary can be, in practice, a highly toxic, low-quality, over-
whelming, and negative experience that differs greatly from watching a political event
without comments or with more in-depth and slow-paced expert commentary.
Table 2 summarizes our hypotheses for frequency, content, and context effects on
experiment participants. First, we anticipated that the introduction of a social chat
stream could be distracting for participants due to the quantity and fast-paced nature
of the comments, leading to a less satisfying and emotionally taxing experience. Our
text analysis results validated our expectation that the social chat had very frequent
comments, and our survey results find that respondents assigned to the social condition
came away with slightly, though not always significantly, less enjoyable, less informa-
tive experiences and felt more anxious and angry than respondents in the ABC News
condition. In addition, while we anticipated the stimulation of the chat could still lead
participants to feel engaged in the video more so than watching the debate without real-
time commentary, we found that respondents in both the social and expert conditions
found the debate significantly less engaging.
We did not find support for our hypotheses that the expert commentary would lead
viewers to find the debate more informative and enjoyable and less emotionally taxing.
As we discuss in the main text, part of the reason for these more muted effects could be
due to the structure and design of the FiveThirtyEight stream, which made it harder
to watch the debate video.
Second, we hypothesized that the content of the streaming chats would influence
name recognition and candidate evaluations. We did not find effects on name recog-
nition. However, we do find evidence that aligns with potential priming effects. Here,
we focus our analysis on our primary treatment– the social chat. Based on content

Scene 30

Frequency
Hyp 1
Debate less enjoyable and informative
Debate more enjoyable and informative
Debate more engaging
Debate more engaging
Hyp 2
More angry and anxious
Less angry and anxious

Content
Hyp 3
Increase in name recognition for candidates men-
tioned most often
Increase in name recognition for candidates men-
tioned most often
Hyp 4
Reduce evaluation toward candidates with nega-
tive primes
Reduce evaluation toward candidates with nega-
tive primes

Context
Hyp 5
Decrease in trust
Increase in trust
Hyp 6
Increase in affective polarization
Decrease in affective polarization
Hyp 7
Infer future poll performance based on sentiment
in chat toward candidate
No change in inferred future poll performance

analysis, candidates who were subject to high frequencies and proportions of negative
comments, such as Biden, Booker, and Harris, were rated significantly lower in feeling
thermometer ratings by respondents in the social condition relative to those in the ABC
News condition.
Lastly, we hypothesized that the negative, toxic nature of the comments may spill
over into evaluations of the overall democratic process and levels of polarization. We
do not find treatment effects on these outcomes. We do, however, find evidence that
people may infer– potentially incorrectly– that the views expressed on the streaming
social chat may reflect the sentiment of the public, more generally. For example, we find
that candidates who received more frequent positive comments, such as Sanders and
Yang, were predicted to do better in the polls by respondents in the social condition.
While this research design achieves high ecological validity as a digital field ex-
periment of a real-world event, it is not without limitations. As previously noted, one
limitation is the ability to accurately assess compliance. Research has shown that survey
respondents often report watching presidential debates more often than what adminis-
trative would suggest (Prior, 2012). Though we attempted to minimize incentives to
provide misleading compliance information, it is possible that not all respondents in the
analysis sample actually watched the debate. It is possible that overstating compliance
could actually understate the effects of streaming commentary on our outcomes. Future
research designs that have the ability to more actively monitor compliance could offer
alternative methods for identifying complier average causal effects.
In addition, while we are confident that streaming chat will continue to be in use in
political broadcasts in the future, our findings may vary depending on the similarity of
the context and nature of the streaming chats. For example, it may be possible for social

Scene 31

chats to have fewer deleterious effects if moderators could control the quantity of user
posts or moderate the content. Contexts in which social chats have more highly curated
streams may lead to different hypotheses. While this may serve as a scope condition on
the results of the study, we believe our theoretical pathways of frequency, content, and
context effects offer a road map for future researchers to develop hypotheses considering
how their settings differ on these dimensions. Even within the current study, we suggest
how the unique features of the social streaming chat may lead to different consequences
from the expert chat.
Overall, our study points to several consequences of streaming chat for political
attitudes by shaping a more negative and less engaging experience that has the potential
to spill over into how viewers evaluate candidates and their viability in elections. These
findings suggest that traditional theories of media effects must account for the potential
role of streaming chat, as it increasingly pervades live political broadcasts.

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