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 on Wednesday pledged not "to be as polite" at the upcoming Democratic debates after being at the center of a tense moment in the first debates when 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.) went after his record on civil rights.

Speaking at a fundraiser in Detroit, Biden said “I’m not going to be as polite this time,” according to The Detroit News.

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“Because this is the same person who asked me to come to California and nominate her in her convention,” he added, referring to Harris.

This week, Biden also exchanged barbs with 2020 hopeful Sen. Cory Booker Cory Anthony Booker3 reasons why Biden is misreading the politics of court packing Bipartisan praise pours in after Ginsburg's death DHS opens probe into allegations at Georgia ICE facility MORE (D-N.J.), who called the former vice president an “architect of mass incarceration" in reference to a 1994 crime bill that Biden helped pass.

“If they want to argue about the past, I can do that,” Biden said at the fundraiser. “I got a past I’m proud of. They got a past that’s not quite so good.”

In the first Democratic primary debates last month, Harris hit Biden over comments about work with segregationist senators as well as his 1970s stance on mandatory busing of black students into majority-white schools. Biden has since apologized for the comments on the segregationist senators.

Biden has long been the front-runner in the crowded Democratic field, but he saw his lead slip in most polling following the first debate. He's among 20 contenders who will take the debate stage later this month.