The best measure we normally have for who “won” a debate is polling that simply asks respondents that question — “Who do you think won?” But candidates don’t enter the debates on equal footing; some are more popular or better known than others. To really understand who was helped or hurt by their debate performance, you’d want both the “before” and “after” pictures. So we’re partnering with Morning Consult to track how feelings about the candidates change by interviewing the same group of voters — people who say they’re likely to vote in the Democratic primary — before and after the first two primary debates.

Voters’ post-debate reactions so far Among all 20 candidates, Kamala Harris, Elizabeth Warren and Julián Castro earned the highest scores for their debate performances relative to their favorability rating before they took the stage, according to the voters in our poll. Bernie Sanders and Cory Booker also rated well, but their scores were more in line with their pre-debate favorability. Meanwhile, voters didn’t exactly think Beto O’Rourke did badly on Night 1, but his grades were underwhelming given his popularity. The over- (and under-) performers How favorably all likely Democratic voters felt about each candidate before the debate vs. how well respondents who watched the debate thought each candidate did

To track which candidates are winning over voters, we asked respondents who they would vote for before and after each debate. That lets us measure not only who gained (or lost) support, but also where that support came from (or went to). Remember, this is only one poll — we’ll need to see other surveys to be sure we know how the debates affected voters — but Harris’s second-night performance doubled her support; she went from just under 8 percent before Night 1 to almost 17 percent percent now. Much of that support came from voters who previously said they were backing Warren or Joe Biden. Speaking of Biden: He lost a bunch of voters — mostly to Harris, but also to Warren, Buttigieg and others. We’ll have to see whether these shifts stick or if voters keep moving around in the next few days and weeks. Who’s changing voters’ minds? Who likely Democratic voters would vote for if the election were held tomorrow, among those who responded to polls conducted both before and after the debates