WASHINGTON _ Sens. Kamala Harris and Elizabeth Warren gained substantial ground after last week's Democratic presidential debates; former Vice President Joe Biden and former Rep. Beto O'Rourke declined.
Biden still leads the field, but has a much shakier position. Harris, at least for now, has moved into rough parity with Sen. Bernie Sanders of Vermont and Warren, the Massachusetts senator, according to post-debate surveys, which have begun providing data on how the debate affected the field of Democratic hopefuls.
Harris, from California, jumped from 8% support nationwide before the debates to 17% afterward, according to a poll by Morning Consult done for the Fivethirtyeight.com website. Biden, by contrast, dropped from 39% to 31%.
Overall support for the other candidates did not shift significantly, although several, including Warren, Sen. Cory Booker of New Jersey and former Housing Secretary Julian Castro, saw significant jumps in the number of Democrats who view them favorably.
Perhaps most ominously for Biden, a second poll, by YouGov for the Huffington Post, found that the share of Democratic voters who see him as "capable of winning the general election" dropped significantly.
Warren and Harris both gained significant ground on that measure, the poll showed. As a result, Biden went from having a big lead on electability to roughly a four-way tie with Warren, Harris and Sanders.
The belief that he is the most electable candidate has buoyed Biden's campaign all spring, and a decline on that measure could pose a major problem for him.
In early May, 70% of Democrats and Democratic-leaning voters told YouGov they saw Biden as capable of winning. In a poll after the debate, that number dropped to 57%.
Harris and Warren went from about 4 in 10 Democratic voters thinking they could win to about half. The share who thought Sanders could win remained steady at slightly less than half, the YouGov poll found.
Warren dominated the first hour of Wednesday night's debate. Thursday night's featured Harris going on offense against Biden over his position on school busing early in his career and his recent expressions of nostalgia for his ability to work with segregationist senators. That attack dominated post-debate news coverage.
Two important caveats apply to all such polls: The impact of a big event, like a debate, often fades over time. And primary elections, unlike general elections, often see rapid shifts in support.
In the YouGov poll, for example, only 38% of voters said they had even a "good idea" of which candidate they'll ultimately vote for. More than half said they were still making up their minds.
Morning Consult, a political polling and research firm, surveyed 7,150 registered voters nationwide who said they plan to vote in the Democratic primaries before the debate. They then re-surveyed 2,041 after the first night of the Democratic debates and 2,485 after the second night.
The survey has a margin of error of 1 percentage point in either direction for the pre-debate numbers and 2 percentage points for the post-debate ones.
YouGov conducted two surveys, June 27-28 and 28-29, each with 1,000 respondents. The estimated margin of error is 3 percentage points in either direction.
