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June 24, 2024

Ask the expert: How much do presidential debates matter?

President Joe Biden and former President Donald Trump are set to square off in the first of two scheduled presidential debates on June 27. While presidential debates are already some of the most anticipated campaign events, several features of this year’s debates –  scheduled much earlier than normal and planned in an unconventional way, along with earlier access to ballots among voters in many key states – have led many to wonder just how much of an impact the debates will have.


Dustin Carnahan is an associate professor in the Department of Communication at Michigan State University’s College of Communication Arts and Sciences whose expertise focuses on how people engage with political information and how that engagement influences their attitudes, beliefs and behaviors. He answers questions about how much debates matter and the potential impact of the new format this year.

What has research shown about the effects of presidential debates?

Headshot of Dustin Carnahan.
Dustin Carnahan is an associate professor in MSU's College of Communication Arts and Sciences.

Since the first nationally televised presidential debate in 1960 — when John F. Kennedy’s careful image management was widely thought, though more recently debated, to have contributed to his election victory over Richard Nixon — scholars have sought to understand how presidential debates influence the electorate.

When it comes to vote choice, research has generally suggested little impact from watching debates. Debate viewers tend to be among the most politically engaged and thereby likely to have their minds made up well before the debate. For these people, debates serve largely as a spectator sport, watched mainly to see how one’s preferred candidate performs and with little to no effect on their opinions of the candidates. That said, some research has suggested that candidates’ debate performances can impact how favorably they are perceived by voters, which can affect the choices of undecided voters. Additionally, a lopsided debate performance or significant gaffe committed by a candidate can have a lasting effect on candidate evaluations.

However, research into potential indirect effects of debates — by commanding significant media attention in the days prior to and after their occurrence — have offered stronger evidence of their influence. One such effect involves learning, whereby voters make gains in their understanding of the issues and candidates after the debates. But while more knowledgeable voters tend to learn more from viewing the actual debates, less knowledgeable voters have been shown to narrow this gap in the days following debates due to debate-related content being hard to avoid even among those who are the least politically engaged.

Do presidential debates still matter in a time of media abundance?

Despite advances in technology and recent social trends that afford people the ability to ‘tune out’ of the political process, such as the rise of streaming platforms and social media, presidential debates still command significant public attention. According to Nielsen ratings, two of the three most viewed presidential debates in American history occurred in 2016 (Donald Trump and Hillary Clinton with 84.4 million viewers) and in 2020 (Donald Trump and Joe Biden with 73.1 million viewers).

Even insofar as people might have a greater ability to avoid the debates themselves due to increasing media options, they are unlikely to get through the day without coming into contact with some debate-related content. Debates dominate news coverage over a 48-hour period both prior to and following the debate, and content across other media platforms are likely to skew more political than normal. For example, during the aforementioned Trump-Clinton debate in 2016, around 17 million debate-related posts were shared on X (formerly Twitter).

What’s unique about the debates in this campaign cycle?

Since the late 1980s, the Commission on Presidential Debates, or CPD, has handled the planning and production of presidential debates in the U.S. As a bipartisan group, the CPD would broker agreements between the major-party presidential candidates and their campaigns on matters such as debate format, topic, location and timing. This usually resulted in a series of three debates (and an additional debate between nominees for vice president) beginning in September, with variations in topic focus and format across the three.

This year, the CPD has been left out of the process altogether. The Republican National Committee withdrew from the CPD in 2022, alleging unfair treatment. And in May, the Biden and Trump campaigns — after some public back and forth — independently negotiated an agreement to hold two debates to take place on June 27 and September 10 without any CPD involvement.

The June debate will mark the earliest general election debate since televised presidential debates began in 1960, made possible by the long-held status of both Biden and Trump as the presumptive nominees for their parties. Additionally, some of the details around the debates differ from earlier CPD-hosted debates; for example, the campaigns have agreed to mute their candidate’s microphones when it is not their turn to speak and there will be no studio audience for the debate.

How might these changes shape the outcome and perceptions of this year’s debates?

Despite these changes, the effects of 2024 debates are unlikely to vary much from prior election years and, given other aspects of this presidential race specifically, are probably less likely to move voters.

While the earlier dates for the debates theoretically offer the candidates a chance to make their case to the public sooner (something noted by both campaigns in circumventing the CPD debate schedule), the vast majority of voters already have entrenched views toward both Trump and Biden — making any debate-related shifts in opinion or learning about the candidates less likely when compared to election years with less familiar candidates. Additionally, given that research has shown that any observable effects of debates often decay rather quickly, any post-debate increases (or decreases) in support for either Trump or Biden will likely fade due to the volume of campaign communication that will likely follow each debate, mostly washing out by the time voters can cast their ballots.

But in a year when each campaign has made no secret of its strategy of questioning the other’s fitness for office, any significant gaffes by either of the candidates during the debate is likely to dominate messaging by the campaigns and in news coverage as evidence of that candidate’s decline. And given the longer period between the first and second debate in 2024 — two months rather than a week or two in a normal debate schedule — attempts at damage control might prove more challenging as a poor performance is likely to linger.

Do debates contribute to the spread of misinformation?

Debates allow candidates the opportunity to make the case for their candidacy directly, without relying on the filtered coverage of the campaigns through news media. For this reason, misinformed or false statements made by the candidates during debates can reach a large audience and circulate broadly before fact-checkers can intervene.

The format of debates — where candidates are allotted a specified amount of time to respond to a moderator’s question — does not allow much opportunity for moderators to fact-check candidates’ statements in real time (when, according to some research, fact-checking messages are likely to have a stronger effect in curbing belief in misinformation). Additionally, research has shown that social media discourse during debates can serve to amplify false and misleading claims made throughout the course of the debate, which can result in boosting audiences’ familiarity with — and, potentially, belief in — these statements.

Fact-checkers and news organizations often spend considerable time addressing specific claims made by the candidates in post-debate news coverage. But while fact-checking messages has been shown in research to be fairly effective in correcting misinformed beliefs, audiences for fact-checking stories overlap little with the audience for the debate — especially among more partisan-minded voters less likely to get their news from a source that challenges their preferred candidate.

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