Washington — President Biden acknowledged that he may not have had the stamina to serve another four years in the White House if he had won reelection. "I don't know," Mr. Biden said in a recent interview with USA Today when asked whether he "would've had the vigor to serve another four years in office."

Instead, however, Biden, who would have been 86 at the end of a potential second term, announced in April that he was running for reelection.