According to the May 22-26 survey, 26 percent of registered voters said placing her on the ticket would make them more likely to vote for Biden, while 23 percent said it would make them less likely to back him. Her positive impact on Biden increased among voters under the age of 45, who view Warren in a more favorable light than they do Biden, as well as black and Hispanic voters.

Warren is the best known of the potential candidates listed in the survey, with 77 percent of voters expressing opinions about her and 91 percent saying they’d at least heard of her. But views about Warren are nearly evenly split, with 38 percent expressing favorable opinions and 39 percent expressing unfavorable opinions, within the poll’s margin of error of 2 percentage points. The poll was conducted among 1,986 registered voters.

Warren, who is more popular than Biden with liberal voters, dropped her own campaign for the Democratic presidential nomination after Super Tuesday in March, and she endorsed Biden’s candidacy in April as part of a show of unity during the same week former President Barack Obama and Sen. Bernie Sanders (I-Vt.) backed his bid.