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Why it’s gotten harder to predict the outcome of the 2024 debates

A new schedule means that the old research and history may not apply.

- June 27, 2024

The first presidential debate takes place tonight. As you probably know by now, Biden and Trump agreed to this June 27 debate and a second one on Sept. 10. They are not going to do the usual three debates overseen by the Commission on Presidential Debates in late September and early October.

Of course, the big question is: In a year of remarkably stable polling, could this debate actually change the state of the race? This is a more complicated question to answer than usual – and we can blame this new debate schedule.

What the previous research says

In August 2012, I wrote a piece summarizing the political science literature on the presidential debates from 1960-2008. Here’s a one-sentence summary: Debates have moved the polls but they have rarely decided the election.

There are two big reasons why. First, the debates took place later in the election season and there weren’t many undecided voters at that point. Second, it has proven tough to “run the table” and win all the debates so convincingly that the winner received a durable benefit. Typically, the candidates have fought to a draw.

By contrast, the party conventions have had larger effects, on average. They have typically occurred earlier than the debates. And because the conventions no longer experience much drama about who’ll be the nominee, they have become infomercials for that candidate. By design, no debate tends to be that one-sided.

Not much about the 2012 debates changed those conclusions, I argued after that election. Mitt Romney did gain a few points after the first debate, but Barack Obama did better in the last two and the end result was basically a wash. There weren’t big debate effects in 2016 or 2020 either, or so we found in our books on those elections.

What’s unusual in 2024

But this year’s schedule creates the potential for something different.

For one, the first debate will take place quite early. There should be more undecided voters than there will be in October. And we know that Joe Biden has work to do rallying Democrats and Democratic-leaning voters. If Biden “wins” the debate – I use scare quotes because these judgments are always subjective – it could boost his standing within the party even before the Democratic convention.

Then there is the Republican convention from July 15-18 and the Democratic convention from August 19-22. This will allow us to observe the potential impact of each. In some years, like 2020, the party conventions are so close together that you can barely see any impact of the first before the second one kicks in. But note also that party conventions have had smaller effects in recent elections.

The second debate on Sept. 10 will also take place earlier than the first debate typically has. So, once again, there could be potential for the polls to move. Moreover, convention bumps sometimes decay and either candidate could benefit from a highly publicized victory in the September debate.

But then…there will be almost 2 months until Election Day. That’s plenty of time for any impact of the final debate to disappear, or another late-breaking event to override the debate’s impact.

It’s also worth noting that Biden has already reserved more time for televised advertising in the fall than Trump has. If those ads have an effect – and there is evidence that advertising can have a small effect – then that could be the ultimate deciding factor in a very close election, not a debate that occurred weeks or months earlier.

In sum, for a long time the presidential campaign calendar followed a pattern: summer party conventions followed by fall debates. That’s what the political science research has studied.

In 2024, we’ll get to study something different – with less predictable consequences. 

For further discussion on the 2024 debates, listen to my conversation with Good Authority Editor Erik Voeten.