Joe Biden appeared intent to follow the rules while defending himself from an onslaught from Democratic challenger Sen. Kamala Harris who attacked him on his civil rights record during Thursday night's debate, abruptly saying, “my time’s up, I’m sorry,” while giving his defense.

The former Vice President was slammed on the debate stage Thursday night, particularly by Harris who said Biden’s earlier comments about being able to work with segregationist senators early in his career were “hurtful.”

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Biden defended himself saying that her comments about his record were a “mischaracterization of my position across the board,” and that he “did not praise racists.”

“I ran because of civil rights,” Biden said, noting that he worked as a public defender after the assassination of Martin Luther King Jr. in 1968. “I continue to believe we need to make fundamental change.”

But the leading 2020 Democratic candidate then stopped abruptly amid the heated exchange, somewhat conceding the attack line. “Anyway,” he said, “my time’s up, I’m sorry.”

“Anyway, my time’s up, I’m sorry.” — Joe Biden

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Harris inflicted serious damage to Biden after she pointed out that Biden’s work with segregationists had a human cost – including to her.

“I also believe — and it is personal — and it was actually very hurtful to hear you talk about the reputations of two United States senators who built their reputations and career on the segregation of race in this country,” Harris said.

“You worked with them to oppose busing,” Harris added, referring to efforts to limit orders for school desegregation by busing. In an emotional moment, she told her own story of being bussed as a little girl in California.

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The Biden campaign tried to mitigate the damage after the debate, with his campaign staff and surrogates defending his civil rights record as “unassailable.”

“If you want to put Vice President Biden’s record on civil rights up against anybody else on that stage, he’ll stand the test of time,” senior adviser Symone Sanders told reporters Thursday night.

“What voters want to hear is what kind of president he’s going to be and how he’s going to tackle these issues in the White House, and I think his record on civil rights is unassailable,” communications director Kate Bedingfield added.

Fox News’ Brooke Singman contributed to this report.