September 30, 2020

Now that the post-debate spinners are busy spinning, I thought it might be useful to see if there’s any evidence that debates sway voters.

Monmouth University polling reported Tuesday that, although just 3% of people surveyed say that they are very likely to hear something that will impact their eventual vote choice, another 10% say it is somewhat likely to happen and 87% say it is not likely. It was about the same in 2016.

Generally, debates do not sway voters.

Harvard Business School research goes against everything you have heard hyped over the last day or two. Data through history shows debates really do not determine election outcomes. Take, for example, a debate from almost exactly four years ago when Hillary Clinton called Donald Trump out for his treatment of women and Trump didn’t have much of a comeback. That debate set viewership records. But, Harvard Business School says:

Every major polling outfit declared Clinton the debate’s victor the next day. But it didn’t make a difference: Trump went on to win the election. That’s because debates have only a negligible effect on voters’ candidate choice, according to new research from Harvard Business School. In fact, 72% of voters make up their minds more than two months before the election, often before candidates square off. And those who shift to a different candidate closer to the election don’t do it following TV debates.

Pew research pegs the number of voters who make up their minds based on debates at about 10%.

(Pew Research Center)

This is not to say debates are worthless. In fact, Pew surveys going back to 1988 show voters find debates “useful” in making their decisions, but not pivotal.

It is not just an American thing. Harvard Business School research mined voter surveys from 61 elections in nine countries — including the U.S., Canada, Germany and the United Kingdom — which included 172,000 respondents, 80% of whom had watched a debate. The study found that about 15% of people decide who they will vote for in the two months before an election. But voters who change their minds about a candidate do not do so because of debates, but instead might change their minds based on new information about a candidate or his/her position on important issues.

The debate itself may not change minds much, but media coverage of the debate can change minds. The media obsession with who “won” and who “lost” has had a measured effect, according to researchers who looked at the 2004 debate between John Kerry and George Bush. Over the years, researchers have also found that journalists tend to award the “winner” title to whoever gets in the best punches, one-liners and snipes, not who explains policy and positions with the greatest depth and clarity.

FiveThirtyEight explains why debates may have an effect in thinning out fields of primary election candidates but don’t change general election outcomes much:

Political science tends to be skeptical of general election debates. The people who are most likely to tune into debates tend to be highly informed and already engaged in politics — and thus already likely to have formed an opinion. This has become especially true in recent years as partisanship has grown stronger.

Washington Monthly took a historical perspective on debates over the decades.

The small or nonexistent movement in voters’ preferences is evident when comparing the polls before and after each debate or during the debate season as a whole. Political lore often glosses over or even ignores the polling data. Even those who do pay attention to polls often fail to separate real changes from random blips due to sampling error.

A more careful study by political scientist James Stimson finds little evidence of game changers in the presidential campaigns between 1960 and 2000. Stimson writes, “There is no case where we can trace a substantial shift to the debates.” At best, debates provide a “nudge” in very close elections like 1960, 1980, or 2000.

An even more comprehensive study, by political scientists Robert Erikson and Christopher Wlezien, which includes every publicly available poll from the presidential elections between 1952 and 2008, comes to a similar conclusion: excluding the 1976 election, which saw Carter’s lead drop steadily throughout the fall, “the best prediction from the debates is the initial verdict before the debates.” In other words, in the average election year, you can accurately predict where the race will stand after the debates by knowing the state of the race before the debates.

Vice presidential debates have even less of an effect on voter decisions. In fact, viewership for the VP debates usually drops way off. The exception was the 2008 debate between Joe Biden and Sarah Palin.

(Pew Research Center)

If debates do not change votes, what does? Researchers found that a personal conversation with another person, even a short conversation with a person who knocks on doors seeking supporters, can make a big difference.

This article originally appeared in Covering COVID-19, a daily Poynter briefing of story ideas about the coronavirus and other timely topics for journalists. Sign up here to have it delivered to your inbox every weekday morning.

Al Tompkins is senior faculty at Poynter. He can be reached at or on Twitter, @atompkins.

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Al Tompkins is one of America's most requested broadcast journalism and multimedia teachers and coaches. After nearly 30 years working as a reporter, photojournalist, producer,…
Al Tompkins

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