Former Vice President Joe Biden Joe BidenPelosi slams Trump executive order on pre-existing conditions: It 'isn't worth the paper it's signed on' Hillicon Valley: Subpoenas for Facebook, Google and Twitter on the cards | Wray rebuffs mail-in voting conspiracies | Reps. raise mass surveillance concerns Fox News poll: Biden ahead of Trump in Nevada, Pennsylvania and Ohio MORE's support among black voters dropped after his performance during last week's presidential debate when he was criticized for his record on race, according to a new Reuters/Ipsos poll.

The survey found that Biden's support went down from 40 percent among black voters in June to 20 percent among black voters in the days following the debate.

Biden took heat from Sen. Kamala Harris Kamala HarrisHundreds of lawyers from nation's oldest African American sorority join effort to fight voter suppression Biden picks up endorsement from progressive climate group 350 Action 3 reasons why Biden is misreading the politics of court packing MORE (D-Calif.) during the debate, where she slammed him for his past remarks about working with two segregationist senators, calling Biden's comments "hurtful."

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Harris also targeted Biden's record on busing black students to majority-white schools during the 1970s.

“On this subject, it cannot be an intellectual debate among Democrats, we have to take it seriously, we have to act swiftly,” Harris said to applause.

Biden hit back at Harris, accusing her of mischaracterizing his positions on the issues.

“I did not praise racists. It is not true, number one. Number two, if you want to have this campaign litigated on who supports civil rights and whether I did or not, I’m happy to do that. I was a public defender. I didn’t become a prosecutor,” Biden said, appearing to hit Harris for her record as a prosecutor.

The exchange appeared to have benefited Harris with the black voting bloc, which is crucial in the Democratic primary.

The Reuters/Ipsos poll found that Harris's support among black voters ticked up to 10 percent, the highest amount out of anyone in the party's primary.

A Quinnipiac University survey released on Tuesday found Biden leading with 31 percent of black Democrats and Democratic-leaning respondents, while Harris held 27 percent support from the group.

The Reuters/Ipsos poll was conducted from June 28-July 1, 2019, among 2,221 adults, including 1,367 Democrats and independents. The survey's credibility interval was 3 percentage points.