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UPDATED Feb. 26, 2020, at 1:10 PM

Who Won The South Carolina Democratic Debate?

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

Seven candidates participated in Tuesday’s debate, hosted by CBS News in Charleston, South Carolina. With the state’s primary looming this Saturday, the stakes were high, and we once again partnered with Ipsos to track how the debate affected likely primary voters’ feelings about the candidates. 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, we plotted how favorably respondents rated the candidates before the debate vs. how debate-watchers rated candidates’ performances afterward. The first thing that stands out from last night’s debate is that Democratic voters were not especially thrilled with anyone’s performance. And as you’ll see, there’s no consistent theme to who voters responded well to, and their responses add up to a somewhat muddled picture of the debate’s effects. That said, Sen. Bernie Sanders and former South Bend, Indiana, Mayor Pete Buttigieg got the highest average performance marks, closely followed by former Vice President Joe Biden and Sen. Amy Klobuchar.

Sen. Elizabeth Warren, on the other hand, got a middle-of-the-pack performance score, but because of her relatively high pre-debate favorability ratings, you’d expect a lot of voters to be predisposed to viewing her debate performance in a positive light, and her score doesn’t look as impressive in comparison. (The same is true for Sanders, even though he got the highest average marks.)

The numbers behind the chart

CandidatePre-debate favorabilityDebate performance
Bernie Sanders64.7%3.0
Pete Buttigieg61.33.0
Joe Biden59.32.9
Amy Klobuchar56.92.8
Elizabeth Warren62.42.8
Tom Steyer49.62.6
Michael Bloomberg46.72.5

In terms of raw debate grades — respondents graded candidates on a four-point scale (higher scores are better) — the clear losers were billionaire activist Tom Steyer and former New York Mayor Michael Bloomberg. However, their scores do look a little better judged against their relatively mediocre pre-debate favorability ratings.

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.’

Tuesday’s debate didn’t trigger any big moves in who respondents said they were considering supporting, like the ones we saw in some previous debates. Warren had the biggest shift, and it’s not all that big — she lost about 2 percentage points in potential support. Klobuchar lost nearly as much. And the only two women on stage were also the only candidates whose potential support declined by more than a point. But no one gained much either. Sanders and Bloomberg had the biggest improvements, and they only added just over 1 point worth of potential supporters. Biden, Steyer and Buttigieg barely budged.

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. Everyone except Warren improved their net favorability rating, though really only Biden’s and, to a lesser extent, Klobuchar’s improved by a meaningful amount. Warren, meanwhile, lost about 2 points in net favorability.

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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

Bernie Sanders
Joe Biden
Michael Bloomberg
Elizabeth Warren
Pete Buttigieg
Amy Klobuchar
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, voters thought Sanders and Biden were most likely to beat Trump. That was still true after the debate, and Sanders even improved his average rating by a hair. But it was actually Steyer whose rating rose the most, improving by just over 2 points. Buttigieg and Warren saw their average scores fall slightly.

Respondents’ average rating of candidates’ chances vs. Trump

CandidatePre-debate averagePost-debate averageDiff.
Tom Steyer27.830.1+2.3
Bernie Sanders59.460.2+0.8
Joe Biden56.056.1+0.1
Michael Bloomberg50.850.3-0.6
Amy Klobuchar37.136.5-0.7
Pete Buttigieg45.444.0-1.4
Elizabeth Warren47.546.0-1.6