It’s another do-or-die election year for Democrats—for real this time—and so the conversation is all about “electability.” Specifically, the ability to beat Donald Trump. For months, the primary beneficiary of this anxiety has been Joe Biden, who is selling himself as a reliable, centrist, course-correcting blue collar warrior. And for the most part, Democrats haven’t really questioned this tautological logic: Biden is leading the polls because he has the best chance of beating Trump, and he has the best chance of beating Trump because he’s leading the polls.

After last week’s two-part Democratic debate, however, the landscape is suddenly looking much different, in a way that suggests Biden’s positive feedback loop could become a vicious spiral. CNN’s first post-debate poll finds Biden still in the lead with 22% support from Democrats or Democratic-leaning voters, but 10 points down from where he was a week earlier. Bernie Sanders also dropped somewhat, to 14%. But Elizabeth Warren and Kamala Harris, who had standout performances on nights one and two, respectively, surged: Warren rose 8 points to 15%, and Harris rose 9 points to 17%. A Huffington Post/YouGov poll found similar results, showing Warren and Harris’s favorability ratings jumping by double digits after the debate, while Biden’s dropped 11 points. (The second-worst performance of the debates was Beto O’Rourke, who was on the blunt edge of an attack from Julián Castro.)

Even more remarkable is what the HuffPost/YouGov survey reveals about intangibles like momentum. When pollsters asked whether the first debate improved or worsened impressions of the candidates, a net 54% of respondents said they were more impressed by Warren, and a net 49% improved their impression of Harris. Biden had a net change of negative 11 points, placing him among other poor debate performers including O’Rourke (-18%), Tim Ryan (-11%), and John Hickenlooper (-12%).

Biden’s still the front-runner, unsurprisingly, but these new numbers suggest he’s vulnerable, especially if his “electability” argument begins to erode. Already, he appears to be losing post-debate support with black voters. If risk-aversion and name recognition initially inflated Biden’s base of support beyond its natural level, perhaps we are beginning to get a more unvarnished view of Biden’s real “electability” in the wild.

Warren and Harris might have their own struggles with perceived “electability,” of course, with both supporting some variation of a health care plan that would effectively eliminate most private insurance, and Harris wading into a controversial debate over reassigning children to different school districts to achieve racial diversity. But all that may prove less important than the optics of electability. On stage last week, Warren was confident and collected, while Harris especially came off as the sort of sophisticated, aggressive debater who might eviscerate Donald Trump. (Biden, who was on the receiving end of Harris’s most pointed attacks, came off looking comparatively weak.) If the quality Democrats most want in a candidate is the ability to best Trump, Harris put on a reassuring performance, while Biden did not. The latest polls suggest that if Biden turns in another debate like the last one, his electability argument could be shot. Absent that patina, can his candidacy stand on its merits?

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