Former President Joe Biden “completely messed up” former Vice President Kamala Harris’ potential 2024 presidential run by opting not to exit the race earlier, a campaign aide claimed.

David Plouffe, who was an influential adviser for Harris’ campaign, placed the blame for her electoral defeat firmly on the ex-president, as noted in a new book co-authored by CNN’s Jake Tapper.

Plouffe — who served as a senior adviser during Obama’s administration — described Harris’ 107-day campaign against Donald Trump as a “complete disaster,” according to an excerpt acquired by The Guardian.

“And it’s all Biden,” he told the authors. “He totally f–ked us.”

Plouffe said he flagged concerns about Biden’s mental and physical ability after receiving a flurry of calls from worried donors in the wake of his catastrophic first debate performance against Trump.

But he said he was repeatedly told the prez could still win another election.

The White House, at the time, also publicly insisted Biden was in good health.

Despite clinging on for three more weeks, Biden ended up dropping out of the race — a move others aides, too, agreed upended Harris’ chances.

“I love Joe Biden. When it comes to decency, there are few in politics like him. Still, it was a disservice to the country and to the party for his family and advisers to allow him to run again,” one senior aide was quoted in the book.

“It was an abomination. He stole an election from the Democratic party; he stole it from the American people,” a prominent Democratic strategist added.