WASHINGTON - Joe Biden joked about his age as he celebrated his 81st birthday on Monday, but the issue is no laughing matter for many voters as he seeks reelection next year.
His birthday renews the focus on the fact that the Democrat is the oldest president in American history -- and that if he wins a second term next year he will be 86 by the time he leaves.
While his aides regularly lash out at those who cast doubt on whether he is too old to be commander-in-chief, Biden likes to suggest that age brings wisdom, or simply takes a light hearted approach.
"It's difficult turning 60," the president said with a chuckle at the annual Thanksgiving turkey pardoning ceremony at the White House on Monday, the same day as his birthday.
"This is the 76th anniversary of this event -- and I want you to know I wasn't there for the first one," he quipped.
But a moment in which he mixed up US singers Taylor Swift and Britney Spears is likely to reinforce impressions among voters who have been concerned by a recent series of trips and slip-ups.
Footage of Biden losing his balance on the stairs of Air Force One has gone viral -- he now uses a shorter flight of stairs -- and he has occasionally given rambling answers during press conferences.
Worse for Biden, voters don't so far have the same concerns about his likely election rival Donald Trump, despite the fact that Trump is 77 and has been known to make similar slip-ups.
Trump warned in a speech in September, for example, that the United States was on the verge of "World War II," and recently said Hungarian Prime Minister Viktor Orban was the leader of Turkey.
- 'Lucid' -
Biden is "not doing a lot wrong" but is struggling to change perceptions on his age -- as well as other issues like the economy -- said David Karol, who teaches government and politics at the University of Maryland.
"He is lucid, but people just have this perception," Karol told AFP.
The White House has been dismissive of opinion polls, with Democrats notching up a series of recent electoral successes. They also point to the fact that Biden beat Trump in 2020 despite Biden being 77 himself at the time.
Yet the numbers make grim reading for the party. Seventy-four percent of people said Biden would be too old to serve a second term, compared to 50 percent for Trump, a recent ABC/Washington Post poll showed.
A Yahoo/YouGov poll found that 54 percent of Americans say Biden no longer has "the competence to carry out the job of president," up from 41 percent before the 2020 election.
Some analysts say Biden's age should not matter.
The issue in general has been unfairly "weaponized" in US politics, said S. Jay Olshansky, a longevity researcher at the University of Illinois at Chicago.
"Aging is not what it used to be," Olshansky told AFP.
"There are very large segments of the population that survive to their eighth decade perfectly capable of being president, or doing whatever they like."
- 'Super-Agers' -
Biden -- and Trump for that matter -- are both likely to be "Super-Agers," a term coined by researchers to describe a small group of people who keep their full faculties until late in life, said Olshansky.
His research has also found that for US presidents, "biological time seems to tick at a slower pace" than for other people, as they apparently thrive on the stress of the job.
That said, Biden's campaign has taken to highlighting Trump's own slip-ups.
Nevertheless, the Democrat's age is bound to come under even deeper scrutiny during a grueling election campaign.
Republicans have trained their fire on the person who is just a heartbeat away from the presidency, should the worst happen: Vice President Kamala Harris.
Harris blazed a trail as the first woman, Black person and person of South Asian descent to hold the vice president's office, but her approval ratings are as bad as her boss's, at under 40 percent.