Expert Commentary

Presidential debates and their effects: Research roundup

2016 updated literature review of political science insights on American presidential debates and their effects.

(NBC screenshot)

The news media often anticipate televised presidential debates as a national event of great importance — a kind of Super Bowl of American democracy. But political scientists have noted that, in contrast to the party conventions, the general election debates do not typically have dramatic effects on voters.

To the extent that the debates are important in terms of persuasion, the format may slightly favor the challenger, about whom the public knows less. The classic example cited is John F. Kennedy (though research from political scientist Sydney Kraus confirms the proverbial notion that he won over the television audience but not the radio listenership). Moreover, gaffes can potentially hurt candidates, as with Gerald Ford’s faulty knowledge of Eastern Europe, George H.W. Bush’s looking at his watch and Al Gore’s audible sighing.

Though reporters often look for a winner and loser, viewers experience the debate differently, making two simultaneous judgments: One, whether or not the candidate seems “big enough” to be president; and two, whether one of the candidates is a better choice.

As political scientist Thomas Holbrook has pointed out, the earlier debates are more powerful in terms of voters’ learning about candidates. In his study “Political Learning from Presidential Debates,” Holbrook states: “The evidence overwhelmingly indicates that the most important debate, at least in terms of information acquisition, is the first debate … The first debate is held at a time when voters have less information at their disposal and a larger share of voters are likely to be undecided.”

Reflecting on the Obama-McCain race of 2008, scholars Kathleen Hall Jamieson and Jeffrey A. Gottfried note that in a “transformed media environment” — where traditional news has ceded ground to non-mainstream media sources — the televised debates continued to play a unique role, as they have through history. “For almost five decades, studies have confirmed the power of presidential debates to increase voter knowledge, and 2008 was no exception,” they write. “The debates’ two-sided clash of competing ideas, unmediated by interpretation from reporters, spiked voter knowledge. In these often disparaged encounters, the presidential and vice presidential nominees took on the deceptions perpetrated by the other side, including those on health care and taxing proposals.”

One noteworthy area of potential impact of the debates is their capacity for what political scientists call “agenda setting”: The salience of a given policy or campaign issue in the public mind can rise as a result, and this may play to the strength or weakness of a particular campaign.

Still, political scientists caution against overestimating the influence and even democratic utility of debates in general; and they put caveats on the ability of social science to measure their true effects. Experimental studies confirm that citizens have a great deal of difficulty making meaningful judgments about two competing messages and assertions of fact, as in a debate setting. Increased voter knowledge on issues, too, does not necessarily equal persuasion, and studies confirm the idea that the debates reinforce partisan positions, with partisans merely becoming more critical. Moreover, the debates are only one communications data point in the campaign — taking place amid a sea of ads and other cultural conversations — and are difficult to disentangle from other dynamics.

As the Pew Research Center has consistently found through the years, nearly two-thirds of voters often say the debates were “very” or “somewhat” helpful in decision-making, while voters say the candidates’ commercials were not helpful. However, some scholars think that, when asked about the influence of debates, citizens are predisposed to assign them outsized significance — they conform to ideas of rational deliberation — and to downplay the power of negative ads and other such opinion-shaping communications.

In any case, the 2008 book Presidential Debates: 50 Years of High-Risk TV, by Alan Schroeder of Northeastern, as well as the 2012 book The Timeline of Presidential Campaigns: How Campaigns Do (and Do Not) Matter, by Robert Erikson of Columbia and Christopher Wlezien of Temple, shed light on these and related issues.

Below is a mix of academic studies that provide diverse insights about debates. For more recent research, please also check out our newest piece focusing on the issue, “US presidential debates: 3 studies journalists should know about.”

Special thanks to political scientists Thomas Patterson of Harvard’s Shorenstein Center, Marion Just of Wellesley College/Shorenstein and John Sides of George Washington University for their input on this overview.



“Presidential Debates: What’s Behind the Numbers?”
Holz, Jo; Akin, Heather; Jamieson, Kathleen Hall. White Paper of the Annenberg Public Policy Center of the University of Pennsylvania, September 2016.

Summary: While the number of households watching presidential and vice-presidential debates has grown substantially since 1960, the proportion of participating households has dropped. This white paper takes a close look at debate viewership, including why audiences watch debates, the changing demographics of viewership and alternate ways to measure viewership. Among the key takeaways from the report: Twenty-nine percent of people surveyed said that presidential debates were more helpful in helping them decide how to vote than news coverage of the campaign, political talk shows, campaign rallies, campaign advertising spots and watching broadcast interviews with the candidates.


“On the Communicative Underpinnings of Campaign Effects: Presidential Debates, Citizen Communication, and Polarization in Evaluations of Candidates”
Cho, Jaeho; Ha, Yerheen Ha. Political Communication, 2012, Vol. 29, No. 2, 184-204. doi: 10.1080/10584609.2012.671233.

Abstract: “Previous research on presidential debates has largely focused on direct effects of debates on viewers. By expanding the context of debate effects to post-debate citizen communication, this study moves beyond the direct and immediate impact of debate viewing and investigates indirect effects of debate viewing mediated by debate-induced citizen communication. Results from two-wave panel data collected before and after the 2004 presidential debates show that, as previous literature has suggested, debate viewing leads to partisan reinforcement and that these debate effects are in part mediated through post-debate political conversation. These findings provide a new layer of complexity to our understanding of the mechanisms underlying debate effects.”


“The Effects of HDTV on Perceptions of Obama and McCain in a 2008 Presidential Debate”
Bos, Angela, L.; van Doorn, Bas W.; Smanik, Abbey C. Communication Research Reports, 2012, Vol. 29, Issue 2. doi:10.1080/08824096.2012.666769.

Abstract: “As high-definition television (HDTV) becomes more prevalent, it may affect how people perceive politicians. This study experimentally tests the effects of HD on people’s perceptions of John McCain and Barack Obama during their second presidential debate, hypothesizing that the HD format will hurt McCain. Consistent with the authors’ expectations, it was found that the HD format negatively influenced global evaluations toward McCain. In addition, HDTV viewers free-listed more negative responses to McCain, including several pertaining to his age. This report discusses why these findings were observed, and implications for candidate strategy and the study of media effects are discussed.”


“Presidential and Vice Presidential Debates in 2008: A Profile of Audience Composition”Kenski, Kate; Jamieson, Kathleen Hall. American Behavioral Scientist, 2011, Vol. 55, No. 3, 307-324. doi: 10.1177/0002764210392166.

Abstract: “In this study, the authors examine the composition of the audiences for the presidential and vice presidential debates in 2008. Results from the 2008 National Annenberg Election Survey show that the size of the vice presidential debate-viewing audience in 2008 exceeded the sizes of the presidential debate-viewing audiences, which is atypical from prior campaign seasons. The same general demographic and political characteristics that have driven political debate viewing in the past were operative during the 2008 presidential and vice presidential debate season, with debate viewing by Blacks being a notable exception. Contrary to our predictions, females were not more likely than males to watch the vice presidential debate. Debate watching was significantly associated with the favorability ratings of the candidates on the Democratic ticket, but it was not associated with the ratings of the Republican nominees.”


“Social Influence on Political Judgments: The Case of Presidential Debates”
Fein, Steven Fein; Goethals, George R.; Kugler, Matthew. Political Psychology, April 2007, Vol. 28, Issue 2.

Abstract: “Four experiments investigated the extent to which judgments of candidate performance in presidential debates could be influenced by the mere knowledge of others’ reactions. In Experiments 1 and 2 participants watched an intact version of a debate or an edited version in which either ‘soundbite’ one-liners or the audience reaction to those soundbites were removed. In Experiment 3 participants saw what was supposedly the reaction of their fellow participants on screen during the debate. Participants in Experiment 4 were exposed to the reactions of live confederates as they watched the last debate of an active presidential campaign. In all studies, audience reactions produced large shifts in participants’ judgments of performance. The results illustrate the power of social context to strongly influence individuals’ judgments of even large amounts of relevant, important information, and they support the categorization of presidential debates as ambiguous stimuli, fertile ground for informational social influence.”


“Social Influence in Televised Election Debates: A Potential Distortion of Democracy”
Davis, C.J.; Bowers, J.S.; Memon A. PLoS ONE, March 2011, Vol. 6, Issue 3, e18154. doi:10.1371/journal.pone.0018154.

Findings: The researchers examine the results of an experiment performed on a random sample of 150 undecided voters the night of the final United Kingdom election debate. The participants were divided into two groups and shown the live debate featuring on-screen graphical “worms” — the real-time visual display of a rising and falling line that responds to audience reactions– that were manipulated by the researchers. One worm favored the incumbent, Gordon Brown, while the other favored Nick Clegg. The third debate participant, David Cameron, was favored by neither worm. Nearly half the participants in the group with the Brown-biased worm (47%) said he won the debate, while 35% and 13% reported that Clegg and Cameron won, respectively. More than three-quarters of the group with the Clegg-biased worm (79%) said he won the debate, compared to 9% and 4% for Brown and Cameron, respectively. These numbers indicate that the groups chose winners “consistent with the bias of the worm that they viewed.” Cameron’s perceived performance in the experiment was much lower than that for the public at large — in a survey, the majority of the U.K. population felt that he won the debate. “His poor performance here is consistent with the fact that the worm was biased against him in both groups.” The proportion of participants who said that they were undecided decreased from around 33% before the debate to 10% after the debate: “Most of these undecided voters were swayed in the direction of the worm.”


“Not Your Parents’ Presidential Debates: Examining the Effects of the CNN/YouTube Debates on Young Citizens’ Civic Engagement”
McKinney, Mitchell S.; Rill, Leslie A. Communication Studies, 2009, Vol. 60, Issue 4. doi: 10.1080/10510970903110001.

Abstract: “During the 2007-2008 U.S. presidential primaries, CNN partnered with YouTube to create the first nationally televised presidential debates where citizens interrogated the candidates via video questions posted to the Internet. The creators of these debates claimed their novel use of Internet technology “would change the face of presidential candidate debates.” The CNN/ YouTube debates were designed expressly to engage citizens in the campaign dialogue, and specifically to engage young citizens who are frequent users of YouTube yet not always among the viewing audience for a televised presidential debate. The current study examines the effects of viewing the CNN/YouTube debates, and particularly the debates’ influence on young citizens’ ‘normative’ democratic attitudes. Building on previous research designed to test differences in debate formats, this study compares young citizens’ reactions to the CNN/ YouTube debates and also to a more traditional presidential debate with candidate questioning controlled by a journalist. Results suggest that while exposure to candidate debates in general yields positive effects on young citizens’ normative democratic attitudes, there was very little difference found in the effects of exposure to the CNN/YouTube debates when compared to a traditional journalist-controlled presidential debate.”


“Will the ‘Real’ Candidates for President and Vice President Please Stand Up? 2008 Pre- and Post-Debate Viewer Perceptions of Candidate Image”
Warner, Benjamin R. American Behavioral Scientist, March 2011, Vol. 55, No. 3, 232-252. doi: 10.1177/0002764210392160.

Abstract: “This study of the 2008 first presidential and vice presidential debate builds on past research on viewers’ perceptions of candidate images. Going back to the Kennedy-Nixon debates in 1960, image research has been conducted in most presidential election cycles. Findings consistently show that viewers enter the debates with perceptions of candidates’ character and leadership qualities and that the debates tend to reinforce rather than change images unless the viewers are undecided or not well informed about a candidate. The results of the 2008 study confirmed trends from past research but also provided some surprises in that most changes in image perception were for senator Joe Biden, the longest-serving public official in the race. The study concludes that media often assume knowledge about candidates that might not exist and that in the 2008 match-ups, the debates did not provide the “game changer” that the McCain-Palin ticket needed to overcome a growing movement toward the Obama-Biden ticket that began shortly before the first debate.”


“The Effect of Fox News and CNN’s Post-debate Commentator Analysis on Viewers’ Perceptions of Presidential Candidate Performance”
Brubaker, Jennifer; Hanson, Gary. Southern Communication Journal, 2009, Vol. 74, Issue 4. doi: 10.1080/10417940902721763.

Abstract: “Television news coverage following a presidential debate often presents the debate as a contest between winners and losers by employing a horse race paradigm. The use of this paradigm can help viewers form their assessments of the candidates’ performances, but its overuse can limit serious campaign discourse on the issues. This study examines the effect of post-debate analysis by two cable news networks on the perceived outcome of a 2004 presidential debate and the perceptions of the candidates, finding perceptions of the outcome differing between viewers of the two networks. This finding contributes to our understanding of viewer interaction with post-debate television coverage by focusing on the importance of the sources of information.”


“A Meta-analysis of the Effects of Viewing U.S. Presidential Debates”
Benoit, William L.; Hansen, Glenn J.; Verser, Rebecca M. Communication Monographs, 2003, Vol. 70, No. 4, pp. 335-350. doi: 10.1080/0363775032000179133.

Abstract: “Televised debates are now an expected component of the American presidential election campaign. A meta-analysis was used to cumulate the research on the effects of watching presidential debates. General campaign debates increase issue knowledge and issue salience (the number of issues a voter uses to evaluate candidates) and can change preference for candidates’ issue stands. Debates can have an agenda-setting effect. Debates can alter perceptions of the candidates’ personality, but they do not exert a significant effect on perceptions of the candidates’ competence (leadership ability). Debates can affect vote preference. Primary debates increase issue knowledge, influence perceptions of candidates’ character, and can alter voter preferences (the effect sizes for these variables are larger in primary than general debates). The effect sizes for the dependent variables with significant effects were heterogeneous (except for effects of debates other than the first on vote preference). No support was found for several possible moderator variables on issue knowledge, character perceptions, candidate competence, and vote preference: nature of subject pool (students, nonstudents), study design (pretest/posttest, viewers/nonviewers), number of days between debate and election, or data collection method (public opinion poll or experimenter data). The first debate in a series had a larger effect on vote preference than other debates, but was not a moderator for other dependent variables. The possibility that other moderator variables are at work cannot be rejected.”


“Voter Decision Making in Election 2000: Campaign Effects, Partisan Activation, and the Clinton Legacy”
Hillygus, Sunshine D.; Jackman, Simon. American Journal of Political Science, 2003, Vol. 47, No. 4, 583-596. doi: 10.1111/1540-5907.00041.

Abstract: “Previous research on presidential debates has largely focused on direct effects of debates on viewers. By expanding the context of debate effects to post-debate citizen communication, this study moves beyond the direct and immediate impact of debate viewing and investigates indirect effects of debate viewing mediated by debate-induced citizen communication. Results from two-wave panel data collected before and after the 2004 presidential debates show that, as previous literature has suggested, debate viewing leads to partisan reinforcement and that these debate effects are in part mediated through post-debate political conversation. These findings provide a new layer of complexity to our understanding of the mechanisms underlying debate effects.”


“Disentangling Media Effects from Debate Effects: The Presentation Mode of Televised Debates and Viewer Decision Making”
Cho, Jaeho. Journalism & Mass Communication Quarterly, June 2009, Vol. 86, No. 2, 383-400. doi: 10.1177/107769900908600208.

Abstract: “This experiment examines whether the presentation mode of televised debates impacts how viewers assess the issues debated. Participants were exposed to a segment of televised debate on either a single- or split-screen. Candidate character and party attachment were more important in how viewers formed opinions of the debated issue with the split-screen than with the single-screen. On the other hand, in the split-screen condition, viewers relied less on pre-existing notions when forming opinions of the debated issue than they did with the single-screen condition. Such modality effects were particularly pronounced for those with low-levels of political attentiveness.”


“Issue Knowledge and Perceptions of Agreement in the 2004 Presidential General Election”
Kenski, Kate; Jamieson, Kathleen Hall. Presidential Studies Quarterly, June 2006, Vol. 36, Issue 2, 243-259. doi: 10.1111/j.1741-5705.2006.00301.x.

Abstract: “Using post-election data from the 2004 National Annenberg Election Survey, this study finds that compared to the 2000 election, candidate issue knowledge was relatively high by the end of the 2004 general election. It argues that just as in 2000, voters’ mistakes in matching presidential candidates with their issue positions benefited Republican incumbent George W. Bush more than Democratic challenger John Kerry. Perceived agreement with Bush exceeded actual agreement on four issues tested. Taking six demographic variables, party identification, and ideology into consideration, knowledge about the candidates’ issue positions mattered, as more informed respondents preferred Kerry to Bush. On the three issue knowledge items on which citizens performed the worst, content analyses indicate that citizens could have learned about the candidates’ positions from the debates as well as press coverage. We offer a number of explanations for these incorrect answers.”


“Television Leads Less Informed Citizens to Vote Based on Candidates’ Appearance”
Lenz, Gabriel S.; Lawson, Chappell. American Journal of Political Science, 2011. doi: 10.1111/j.1540-5907.2011.00511.x.

Findings: In gubernatorial races, a voter who watches more television places slightly more importance (7%) on a candidate’s appearance than the typical voter. Among these higher-intensity viewers, those identified as “low-knowledge” voters were 11% more likely to judge a gubernatorial candidate by his or her appearance. A similar effect was seen in Senate races during the same period, with 16% of “low-knowledge,” higher-intensity TV viewing voters more likely to judge a candidate based on appearance. Put simply, “Candidate appearance matters more … when less-informed individuals watch a good deal of television.” Low-information voters are 10% more likely than their high-information counterparts to judge a candidate’s abilities on his or her looks; low-information, higher-intensity TV viewing voters are 32% more likely to judge a candidate by appearance. In summary, “Among low-knowledge individuals (bottom quartile), a 10 percentage point increase in their appearance advantage leads to only a 0.8 percentage point increase in vote share among those who watch little or no television, a 2 percentage point increase among those with average TV viewing, and a 4.8 percentage point increase among those who watch the most TV. Since 10 percentage point differences in appearance advantage are common, as one standard deviation is 20, the effect is considerable.” There is no appreciable difference between high-information voters who don’t watch much TV and those who do: “Television fails to exacerbate the appearance effect among more knowledgeable individuals.”


Keywords: research roundup, presidency, polarization, campaign issues, viewership, audience


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