“Vice President Biden is in excellent physical condition,” said Dr. O’Connor, a retired Army colonel, who served as a White House physician and was named physician to the vice president in 2009. “He is more than capable of handling the rigors of the campaign and the office for which he is running.”
Biden aides grumble there are far fewer questions about the age of his fellow candidates in their 70s, noting that Mr. Biden is in strong physical shape for his age.
“The person he’s going to be running against is about the same age,” said Representative Cedric Richmond of Louisiana, a Biden campaign co-chairman, in reference to Mr. Trump. He also noted that his candidate is in better shape and, alluding to the president’s erratic behavior, is “of sound mind.”
Or as John Morgan, a Florida donor who hosted the former vice-president at his home for a fund-raiser this spring, put it: “Can you see Donald Trump jogging?”
Mr. Biden’s allies describe him as a fitness fanatic and reasonably disciplined eater who also enjoys ice cream and cheeseburgers. As vice president, he favored staples like yogurt and juice, salads with protein and for dinner, pasta or fish, said John Flynn, who served as military aide, personal aide and as a senior adviser to the then-vice president over the course of about five years. Mr. Flynn added that he sometimes briefed Mr. Biden at the gym.
“I work out every morning,” Mr. Biden said earlier this month. “I usually work on the Peloton bike, and I lift.”
His aides insist that Mr. Biden has more energy than they do. At a South Carolina fish fry last month, allies note, he outlasted rivals in greeting voters late into the night. Senator Lindsey Graham, the South Carolina Republican, has also vouched for Mr. Biden’s vigor, saying on CBS in April, “if you travel with Joe Biden, you won’t think he’s too old.”