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UPDATED Dec. 20, 2019, at 1:40 PM

Who Won The December Democratic Debate?

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

Just seven candidates qualified for Thursday’s debate, making it the smallest face-off yet, and we once again partnered with Ipsos to track how the debate, hosted by “PBS NewsHour” and Politico, affected likely primary voters’ feelings about the candidates on the stage. The FiveThirtyEight/Ipsos poll, conducted using Ipsos’s KnowledgePanel, interviewed the same group of voters twice, once 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 Thursday night, we plotted how favorably respondents rated the candidates before the debate vs. how debate-watchers rated candidates’ performances afterward. And if it’s hard to see a breakout star in this round, that’s because Joe Biden, Elizabeth Warren and Bernie Sanders are clustered very close together. Although Biden received the highest marks, his high pre-debate favorability rating means we expected a lot of voters to be predisposed to viewing his debate performance in a positive light. It is notable, though, that Biden received high marks, as he hasn’t fared nearly as well in some of our other post-debate surveys. Warren and Sanders were tied for a close second place in their debate grade, but, like with Biden, their pre-debate favorability ratings meant we figured voters would rate them positively — Warren was even slightly worse than expected. Andrew Yang and Amy Klobuchar, on the other hand, did better than expected given their pre-debate favorability ratings, earning the third-highest marks. Being the focus of several of his rivals’ attacks seems to have hurt Pete Buttigeg; he got low marks relative to how well-liked he was going into the debate. Tom Steyer also failed to make a positive impression.

The numbers behind the chart

CandidatePre-debate favorabilityDebate performance
Joe Biden66.3%3.2
Bernie Sanders65.13.1
Elizabeth Warren64.83.1
Andrew Yang55.53.0
Amy Klobuchar54.33.0
Pete Buttigieg62.52.9
Tom Steyer50.42.7

In terms of raw debate grades — respondents graded candidates on a four-point scale (higher scores are better) — Biden got the highest average score, closely followed by Sanders and Warren, who tied for second; Yang and Klobuchar also did well.

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.’

The biggest winner in terms of attracting potential voters was clearly Klobuchar, who gained a little over 4 points in the share of respondents who said they were considering voting for her. Biden and Sanders also gained nearly 2 points each in potential support. No one seems to have lost any potential supporters, although candidates like Yang, Warren and Buttigieg made only small gains of less than 1 point each.

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. And perhaps unsurprisingly, it was the less-well-known candidates who gained the most: Yang and Klobuchar saw the largest jumps in net favorability (favorable rating minus unfavorable rating) — 6.3 points and 6.1 points, respectively. Most of the other candidates made more modest gains of 2 or 3 points; Buttigieg was the only candidate whose net favorability fell — it dropped by about 2 points.

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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.’

Voters were also asked what matters more to them — a candidate who agrees with them on most issues or someone who would have a good chance of defeating President Trump — and as you can see, there was only a slight change in the post-debate numbers compared to pre-debate responses. After Thursday night, the share of likely Democratic primary voters who prioritized issues over electability ticked up a couple points, but many voters still really want a candidate who can beat Trump.

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
Bernie Sanders
Elizabeth Warren
Pete Buttigieg
Amy Klobuchar
Andrew Yang
Tom Steyer

Finally, we asked respondents to estimate each Democrat’s chances of defeating Trump, from 0 percent (no chance) to 100 percent (certain to win). 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 December debate, but, as you can see below, his average dropped by roughly half a point. Klobuchar, on the other hand, made the largest gains by this metric, with her average rating increasing by 4 points. Other candidates, like Yang and Steyer, saw more modest increases, while Buttigieg saw a small downtick.

Respondents’ average rating of candidates’ chances vs. Trump

CandidatePre-debate averagePost-debate averageDiff.
Amy Klobuchar32.336.4+4.1
Tom Steyer30.131.9+1.7
Andrew Yang32.833.9+1.0
Elizabeth Warren53.654.5+0.8
Bernie Sanders56.656.8+0.2
Joe Biden67.166.6-0.6
Pete Buttigieg45.244.4-0.8