The former vice president, Kamala Harris, says in an upcoming memoir about her failed presidential bid she was “angry and disappointed” in President Biden, claiming she received a jarring phone call just hours before a pivotal debate with President Trump in which he told her that his brother’s influential allies were turning their backs on her campaign.

The account is included in “107 Days,” a campaign memoir due to be released next week. Ms. Harris writes that she was in a Philadelphia hotel room prepping for a make-or-break moment in her campaign when she received a call from Mr. Biden, who began by offering well-wishes for the debate. Things turned awkward, she says, when Mr. Biden asked if she would be back in the City of Brotherly Love before Election Day.

“My brother called. He’s been talking to a group of real power brokers in Philly,” Ms. Harris says in her book, excerpts of which were published in the Guardian. She says Mr. Biden offered up several names and asked if she knew them. She responded that she did not.

“Then he got to his point. His brother had told him that those guys were not going to support me because I’d been saying bad things about him. He wasn’t inclined to believe it, he claimed, but he thought I should know in case my team had been encouraging me to put daylight between the two of us.”

Ms. Harris says she asked Mr. Biden to connect her with the group but that Mr. Biden had moved on, trying to put a positive spin on his dismal debate performance three months earlier.

“Joe then rattled on about his own former debate performances,” she writes. “‘I beat him the other time; I wasn’t feeling well in that last one.’ He continued to insist that his debate performance hadn’t hurt him much with the electorate.” 

“I was barely listening.”

The former vice president says that she considered her debate that evening with Mr. Trump to be akin to “a big prizefight” and that she had needed to be at the top of her game.

“I just couldn’t understand why he would call me, right now, and make it all about himself. Distracting me with worry about hostile powerbrokers in the biggest city of the most important state,” she writes, adding that her husband, Doug Emhoff, attempted to get her focus back onto the task at hand.

“[He]could see how angry and disappointed I was. ‘Let it go,’ he said. He knew I had to redirect my focus. ‘Don’t worry about him. You’re dealing with Trump. Let it go.’”

Throughout the campaign and after, Ms. Harris avoided criticizing Mr. Biden, and defended him against questions about his mental acumen. But in her memoir, she details tensions between the two, including a moment from 2022 after the Supreme Court overturned the Roe v. Wade decision.

“Joe struggled to talk about reproductive rights in a way that met the gravity of the moment,” she said.

Ms. Harris admits she worried about Mr. Biden’s campaign performance, even while believing he could still govern effectively.

“His voice was no longer strong, his verbal stumbles more frequent.”