President Biden acknowledged in a new interview released on Wednesday that he might not have had the vitality to serve another four years in office, even as he insisted that he could have won re-election had he stayed in the race.
Mr. Biden, 82, who abandoned his bid for a second term in July under enormous pressure from Democrats panicked over his faltering debate performance against former President Donald J. Trump, maintained that he was still in good enough shape to run the country as he finishes his term.
“So far, so good,” he told USA Today. “But who knows what I’m going to be when I’m 86 years old?”
That was exactly the point many Democrats raised privately for months before the issue exploded into public view with the televised debate in June, when a frail-looking Mr. Biden struggled to finish sentences and at times appeared blank or confused.
Until then and even after the debate for a few weeks, Mr. Biden and his closest advisers argued that he was still vigorous enough to beat Mr. Trump despite polls showing widespread doubts about his capacity, including among Democrats. Even now, after his stand-in, Vice President Kamala Harris, lost to Mr. Trump, Mr. Biden said he would have prevailed.
“It’s presumptuous to say that, but I think yes,” Mr. Biden said in the interview. But when the question turned to whether he would have been able to bear the extraordinary burdens that come with the presidency until age 86, Mr. Biden, already the oldest president in American history, conceded doubts that he rarely admits to. “I don’t know,” he said.