That drew a response from California Sen. Kamala Harris, an African American woman on stage alongside Biden and other hopefuls Wednesday in Atlanta.
Harris interjected by saying that "the other one is here." Sen. Cory Booker, who is also black, said to Biden: "That's not true."
Biden quickly stated: "I said the first."
Harris' campaign tweeted moments later: "Proud to be the second Black woman elected to the U.S. Senate."
Proud to be the second Black woman elected to the U.S. Senate. #DemDebate— Kamala Harris (@KamalaHarris) November 21, 2019
Biden was arguing that he has support from black voters, who are critical to a Democratic victory. He says that "they know me."
Carol Moseley Braun, a Democrat, was the first African American woman elected to the U.S. Senate. She represented Illinois from 1993 until 1999. Moseley Braun lost her re-election bid and was later appointed to serve as the U.S. ambassador to New Zealand.
The Associated Press contributed to this report.