Sen. Kamala Harris confronted former Vice President Joe Biden over his civil rights record in one of the most tense moments of Thursday’s Democratic primary debate. And she used her own story as the lone black person on stage.

“I do not believe you are a racist, and I agree with you when you commit yourself to the importance of finding common ground,” she said. “But it was hurtful to hear you talk the reputations of two United States Senators who built their reputations and career on segregation of race in this country.”

She continued: “And it was not only that, but you also worked with them to oppose busing. And you know, there was a little girl in California who was a part of the second class to integrate her public schools, and she was bused to school every day. And that little girl was me.”

Earlier this month, Biden came under fire for fondly recalling politics in the 1970s, saying it was an era in which he was able to find common ground across lines—even when that included working with staunch segregationists like Sens. James Eastland and Herman Talmadge.

In response to Harris’ attack, Biden said her comment was a “mischaracterization of my position across the board.” He then went after Harris’ history as a prosecutor. He also defended his position on busing.

“The fact is that in terms of busing, the busing, I never — you would have been able to go to school the same exact way because it was a local decision made by your city council,” he said.

Asked by Harris if he agreed today that he was wrong to oppose busing in the past, Biden disagreed. “I did not oppose busing in America. What I opposed is busing ordered by the Department of Education,” he said. “That’s what I opposed.” Biden said Harris was part of a class that integrated her school in Berkeley, Ca. because of a failure on the part of the local city council.

Harris responded: “That’s where the federal government must step in … Because there are moments in history where states fail to preserve the civil rights of all people.”

Biden’s record on busing and school desegregation

While Biden said he disagreed with segregationists like Eastland on other matters of civil rights, they found common ground on opposing using busing to integrate schools.

When Biden was relatively new to the Senate in the 1970s, the issue of whether to send black students to majority-white schools and white students to majority-black schools was an intensely controversial one. Biden took a strong stand opposing busing integration in schools, and it is a position he has stood by even 40 years later.

A spokesman for Biden recently told the New York Times that the former Vice President did support integrating schools, but he did not believe busing was the best way to get that done. Still, Harris was correct that Biden worked with conservative Senators who had very different goals in opposing busing.

In 1975, Biden supported an anti-busing measure from civil rights opponent Sen. Jesse Helms. Biden then introduced a proposal in 1976 to stop the Justice Department from using busing to desegregate schools and supported a similar amendment in 1977 before introducing another bill that year opposing court-ordered busing. He also directly sought support from Eastland, one of the segregationist Senators that Harris referenced, in these efforts. In letters revealed by CNN earlier this year, Biden wrote to Eastland expressing his thanks for Eastland’s support and displaying a fervent opposition to the idea of busing. This common opposition to busing was part of why Eastland became interested in Biden, according to the Times.

But Biden also emphasized his stance on busing on his own. In a 1975 interview with a Delaware newspaper that was re-surfaced by the Washington Post in March 2019, he explained why he thought the government should have a limited role in desegregating schools.

“We’ve lost our bearings since the 1954 Brown vs. School Board desegregation case,” he said. “To ‘desegregate’ is different than to ‘integrate.'” In the interview, Biden called busing plans racist, and said the integration plans “are really just quota systems.”

He added: “I do not buy the concept, popular in the ’60s, which said, ‘We have suppressed the black man for 300 years and the white man is now far ahead in the race for everything our society offers. In order to even the score, we must now give the black man a head start, or even hold the white man back, to even the race.'”

Write to Mahita Gajanan at mahita.gajanan@time.com and Abigail Abrams at abigail.abrams@time.com.