Do Debates Matter? Maybe This Time

Editor’s Note: This article previously appeared in a different format as part of The Atlantic’s Notes section, retired in 2021.
The Lincoln-Douglas debates of 1858, one year after The Atlantic’s founding, “mattered” in American history because of the ideas they advanced. (Stephen Douglas held onto his seat in the Senate; not long afterward Lincoln began his campaign for the presidency.) Is it possible that the Clinton-Trump debates of 2016, or Year 159 of The Atlantic’s history, will also matter? (Robert Marshall Root painting, via Illinois Periodicals Online)

In my my article on this year’s presidential debates, I pointed out that these high-drama election-year rituals seem important to mere citizens and journalists. But political scientists have long claimed there’s no proof that they’ve actually changed presidential election results.

Maybe they’ll say something different when this year’s results are in. At face value, it certainly appears that the first Clinton-Trump debate—a month ago today—marked a clear shift in Hillary Clinton’s favor and against Donald Trump.

Below is a screenshot of the timeline for the “polls-plus” prediction of the election’s outcome, from FiveThirtyEight. I’ve added the big black arrow to mark the first debate. The thinner vertical lines to the right are the other two debates, each one of which went badly for Trump and, from this chart, seemed to reinforce Clinton’s lead.

As a reminder: debate #2 was the town hall, in which Trump loomed up behind Clinton like a lurker, and #3 was the debate of “such a nasty woman” and “keep you in suspense” (about accepting election outcome).

The screenshot below from the NYT’s “Who Will Be President” tracker shows something similar. Again, the black bar marks the first debate.

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For one more way to look at this question, which is less immediately obvious in graphic terms but cumulatively more convincing, please check out this recent tweet-storm by the U. Michigan economist Justin Wolfers.

He tested the debates-matter hypothesis in an ingenious way, by tracking the movement of financial and futures markets while the first debate was actually underway. As the debate wore on, Wolfers found, a wide variety of markets quickly adjusted to the levels they would have if Hillary Clinton became president. For instance, during the debate the Mexican peso rose sharply in value, based on the declining likelihood that U.S.-Mexico trade would be disrupted by a Wall or other limits under a President Trump.

The point of the study, again, was that the back-and-forth of the debate, in itself, convinced people placing financial bets that Donald Trump was not going to become president. They adjusted their financial bets accordingly.

Prediction markets are obviously fallible; in the most famous recent case, they missed the Brexit vote. And financial markets as a whole tend to overreact to short-term news. But together with the longer-term polling trends, Wolfers’s study may reinforce the hypothesis I mentioned a week ago: that this time, the debates really have mattered.