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.) picked up endorsements from two Congressional Black Caucus (CBC) members on Sunday following a strong performance in the first Democratic presidential debate late last week.

Reps. Frederica Wilson Frederica Patricia WilsonHarris calls it 'outrageous' Trump downplayed coronavirus House passes bill establishing commission to study racial disparities affecting Black men, boys Florida county official apologizes for social media post invoking Hitler MORE (D-Fla.) and Bobby Rush Bobby Lee RushCongress should investigate OAS actions in Bolivia Rep. Bobby Rush introduces legislation focused on addressing racism, lack of diversity in the federal government House Democrat introduces bill to replace Confederate monuments nationwide MORE (D-Ill.) on Sunday became the fifth and sixth members of the CBC to endorse Harris, who is black.

ADVERTISEMENT

Harris has been competing with fellow Democratic contender 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.) for endorsements from members of the powerful group.

African American voters are a key constituency in the Democratic Party, and securing the support of black lawmakers would give a significant boost to either campaign.

Harris has seen her stock in the Democratic primary rise significantly since her debate performance in Miami.

The California lawmaker came out a big winner in polling and fundraising following what many considered a standout debate performance.

Harris's breakout moment came in a heated back-and-forth with 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 during which she criticized the former vice president's opposition to federally mandated busing to desegregate schools.

"There was a little girl in California who was part of the second class to integrate her public schools, and she was bused to school every day," Harris said to Biden. "That little girl was me."

Biden called Harris's criticism a "mischaracterization" of his views and said his issue was with the Department of Education administering busing policies.

— Scott Wong contributed to this report.