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UPDATED Oct. 16, 2019, at 1:36 PM

Who Won The Fourth Democratic Debate?

We partnered with Ipsos to poll voters before and after the candidates took the stage.

If something is going to shake up the race before the Iowa caucuses, it’s likely to be a debate. So we partnered with Ipsos to once again track how Tuesday’s debate, hosted by CNN and The New York Times, affected likely primary voters’ feelings about the candidates. The FiveThirtyEight/Ipsos poll, conducted using Ipsos’s KnowledgePanel, interviewed the same group of voters twice, on either side of the debate, to capture both the “before” and “after” picture.

Who won the debate?

The over- (and under-) performers

How favorably all likely primary voters felt about each candidate before the debate vs. how well respondents who watched the debate thought each candidate did

To better understand which candidates did well or poorly Tuesday night, we plotted how favorably respondents rated the candidates before the debate vs. how debate-watchers rated their performance. And one thing that immediately stands out is that some of the lower-tier candidates did better than we’d expect based on their favorability ratings. Both Pete Buttigieg and Amy Klobuchar were relatively well-liked going in, but got even higher marks for their debate performance than their popularity alone suggests they should. In fact, Buttigieg received the third-highest debate performance grade. Only Bernie Sanders and Elizabeth Warren scored higher, but their debate performances were more in line with their pre-debate favorability ratings. Joe Biden, notably, didn’t have that bad of an overall debate grade, but it was still a bit lower than we might expect given how well-liked he is.

The numbers behind the chart

CandidatePre-debate favorabilityDebate performance
Elizabeth Warren71.9%3.2
Bernie Sanders66.33.1
Pete Buttigieg64.03.1
Joe Biden68.23.0
Amy Klobuchar54.62.9
Kamala Harris61.22.8
Cory Booker59.42.8
Andrew Yang55.32.7
Beto O’Rourke57.72.6
Julián Castro53.52.5
Tom Steyer48.72.5
Tulsi Gabbard46.72.4

In terms of raw debate grades — respondents graded candidates on a four-point scale (higher scores are better) — Warren and Sanders did best, closely followed by Buttigieg, Biden and Klobuchar. Julián Castro, Tom Steyer and Tulsi Gabbard received the worst marks, on average.

How the race changed

Who gained (and lost) support

Share of respondents who are considering voting for each candidate

Before debateAfter debate

Respondents could pick multiple candidates or ‘someone else.’

Going into the fourth debate, we said that the field may be consolidating around two or three candidates, but that hasn’t stopped many voters from considering multiple candidates. And as you can see in the chart above, that seems to be especially true after Tuesday night. Buttigieg got the biggest increase — 4.5 points — in the share of likely Democratic primary voters who are considering supporting him. Klobuchar and Warren also got meaningful bumps, gaining 3.6 points and 2.6 points, respectively. Interestingly, Sanders was the only candidate to lose potential supporters, but it was a tiny drop (less than a percentage point).

The popularity contest

Candidates' favorable and unfavorable ratings among likely primary voters

Before debate
After debate

We also asked likely Democratic primary voters how favorably they felt about each candidate both before and after the debate. Klobuchar and Buttigeg saw the largest jumps in net favorability (favorable rating minus unfavorable rating) — 3.2 points and 2.6 points, respectively. And among the polling front-runners, both Warren and Sanders’s net favorability ratings improved by more than 2 points, while Biden’s increased by a little over 1 point. Beto O’Rourke saw the biggest decrease in net favorability, dropping by 5.7 points, and both Gabbard and Castro fell sharply in voters’ eyes, too.

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Which matters most: policy positions … or winning?

Share of likely primary voters by whether, if they had to choose, they’d prefer a candidate who has a good chance of beating Trump or a candidate who agrees with them on the issues

Excludes respondents who chose ‘I don't know enough to say.’

We also asked voters what matters more to them — a candidate who agrees with them on most issues or someone who would be a strong candidate against President Trump — and as you can see, there was essentially no change from before the debate.

Who voters think can beat Trump

Respondents’ estimates of the likelihood, from 0 percent (impossible) to 100 percent (certain), that each candidate would beat Trump if they were the Democratic nominee

Joe Biden
Elizabeth Warren
Bernie Sanders
Kamala Harris
Pete Buttigieg
Cory Booker
Beto O’Rourke
Amy Klobuchar
Andrew Yang
Julián Castro
Tom Steyer
Tulsi Gabbard

We asked respondents to estimate each Democrat’s chances of defeating Trump, from 0 percent (no chance) to 100 percent (certain to win). (And for this debate, we specifically asked people to “imagine the primary is over and each of the following candidates has won the Democratic nomination.”) Going into the debate, as in other general-election polls, Biden was the candidate voters thought was most likely to beat Trump, on average. He still leads on that question after the fourth debate, but, as you can see below, Biden’s average rating dropped by almost 2 points. O’Rourke didn’t fare well either; his average electability rating fell be nearly 3 points — the most of any candidate. Klobuchar was the only candidate whose average score improved.

Respondents’ average rating of candidates’ chances vs. Trump

CandidatePre-debate averagePost-debate averageDiff.
Amy Klobuchar31.832.9+1.1
Tom Steyer24.524.50.0
Pete Buttigieg43.342.7-0.6
Elizabeth Warren62.061.4-0.6
Kamala Harris45.745.0-0.7
Andrew Yang31.530.7-0.9
Bernie Sanders59.058.0-1.0
Cory Booker38.737.7-1.0
Tulsi Gabbard23.222.1-1.0
Julián Castro31.129.5-1.6
Joe Biden70.068.2-1.8
Beto O’Rourke39.736.8-2.9