Biden told Pete Buttigieg 'that was some f---ing bulls---' on stage after a combative debate exchange with Kamala Harris, according to a new book

• Joe Biden was stunned when Kamala Harris attacked him during a Democratic primary debate in 2019.
• "Well, that was some f---ing bulls---," he told Pete Buttigieg, according to a new book.
• The book dives into the story of that primary debate in June 2019.

Long before they became the president and the vice president, Joe Biden and Kamala Harris were rival Democratic candidates duking it out on the debate stage.

One of their most memorable exchanges unfolded in June 2019 when Harris challenged Biden, then the frontrunner, over his record on busing and race.

Stunned, Biden leaned over during a commercial break to tell Pete Buttigieg, "Well, that was some f---ing bulls---," according to "Battle for the Soul: Inside the Democrats' Campaigns to Defeat Trump," a new book by the Atlantic writer Edward-Isaac Dovere.

In an excerpt of the book published by Politico on Wednesday, Dovere told the inside story of that tense primary debate.

Shortly before the debate, Biden was criticized for boasting about his reputation for working across the aisle. During a fundraiser in New York City, he spoke about his career as a senator and described legislating alongside segregationist lawmakers.

"Well, guess what? At least there was some civility. We got things done. We didn't agree on much of anything. We got things done," Biden said.

Harris had been readying an attack on Biden over his comments, and her team had compiled opposition research to hit him hard on racial issues, according to Dovere. When the topic was brought up on stage, Harris' aides advised her to go for the jugular.

"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 told Biden. "But I also believe, and it's personal - it was 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.

"And it was not only that, but you also worked with them to oppose busing," Harris continued. "And, you know, 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. And that little girl was me."

Biden sought to defend himself and said Harris' comments were a mischaracterization. When the debate cut to commercial, Dovere reported, Biden offered his candid reaction to Buttigieg, whom he then hardly knew. Buttigieg now serves as Biden's transportation secretary.

The moment now appears to be a blip in Biden and Harris' relationship. Harris dropped out of the race in December 2019, and Biden announced her as his vice-presidential pick in August 2020. At the time, they downplayed the combative exchange.

"It was a debate," Harris said.