WASHINGTON (AP) — People in their 80s lead countries, create majestic art and perform feats of endurance. One entered the record books for scaling Mount Everest. It's soon time for Joe Biden, 80 on Sunday, to decide whether he has one more mountain to climb — the one to a second term as president.

Questions swirl now, in his own party as well as broadly in the country, about whether he's got what it takes to go for the summit again.

The oldest president in U.S. history, Biden hits his milestone birthday at a personal crossroads as he and his family face a decision in the coming months on whether he should announce for reelection. He'd be 86 at the end of a potential second term.

Biden aides and allies all say he intends to run — and his team has begun quiet preparations for a campaign — but it has often been the president himself who has sounded the most equivocal. "My intention is that I run again," he said at a news conference this month. "But I'm a great respecter of fate."

"We're going to have discussions about it," he said. Aides expect those conversations to pick up in earnest over Thanksgiving and Christmas, with a decision not until well after New Year's.

Biden planned to celebrate his birthday at a family brunch in the White House on Sunday.

To observe Biden at work is to see a leader tap a storehouse of knowledge built up over a half century in public office as he draws on deep personal relationships at home and abroad, his mastery of policy and his familiarity with how Washington works or doesn't. In short, the wisdom of the aged.

"There is something to be said for experience," said Dartmouth College historian Matt Delmont as he noted the dozens of global leaders in their 80s.

But to observe Biden is also to see him walk now often with a halting gait, in contrast to his trotting on stage on election night 2020.

It is to see him take a pass on a formal dinner with other world leaders without a real explanation, as happened on his trip abroad this past week, when he twice spoke of visiting Colombia when he meant Cambodia. Some supporters wince when he speaks, hoping he gets through his remarks OK.

House Speaker Nancy Pelosi's decision, at age 82, to pull back from leadership and let a new generation rise may spill over into Biden's thinking and that of his party as Democrats weigh whether they want to go with a proven winner or turn to the energy of youth.

Among the questions Pelosi's move raises, said Kathleen Hall Jamieson, an authority on political communications at the University of Pennsylvania: "Even if one is highly competent and successful, is there a point at which one should step aside to give others the opportunity to lead just as others stepped aside to make it possible for you to do so?

"Pelosi's decision makes such questions more salient in the context of Biden's 2020 statement that he was the bridge to a new generation of leaders."

Biden's verbal flubs have been the stuff of legend throughout his five-decade political career, so sussing out the impact of age on his acuity is a guessing game for "armchair gerontologists," as Dr. S. Jay Olshansky, an aging expert, puts it.

In the distorted mirrors of social media commentary, every slip is magnified into supposed proof of senility. A moment of silent reflection by Biden in a meeting is presented as the president nodding off. All of that went into Donald Trump's quiver of falsehoods when he announced Tuesday he will seek the presidency again.

Some allies see Biden's blunders as an increasing vulnerability in the eyes of voters as he's grown older.

In an AP VoteCast survey of the electorate this month, fully 58% of voters said he does not have the mental capability to serve effectively as president. That was a grim picture of his standing now, not just looking ahead to another potential term. Only 34% said he's a strong leader.

Those findings come alongside notably low approval ratings in league with Trump's at this point of their presidencies.

Two months before the 2020 election, Olshansky, at the University of Illinois, Chicago, published a paper that predicted both Biden and Trump were bound to maintain their good health beyond the end of this presidential term.

Based on a scientific team's evaluation of available medical records, family history and other information, the paper further concluded that both men are probably "super-agers," a subgroup of people who maintain their mental and physical functioning and tend to live longer than the average person their age.

Nothing has changed Olshansky's mind about either of them.

"While President Biden may chronologically be 80 years old, biologically he probably isn't," he said. "And biological age is far more important than chronological age." He calls Biden a "classic example of everything that's good about aging ... and so his age, I think, should be almost completely irrelevant."

Biden is already in the club of high achievers for people his age. Unlike 92% of people 75 and over in the U.S., he still has a job, not to mention a mightily demanding one.

And he's been on a roll. The November elections produced the best result for a Democratic president's party in midterms in decades — despite the poison pill of high inflation — as Democrats kept control of the Senate, narrowly lost the House in defiance of expectations of a rout, and won several competitive governors' races in key states.

The president also sealed a string of consequential legislative victories in recent months, on climate, infrastructure, health care expansion, military aid to Ukraine and more.

Biden says he begins most days with an 8 a.m. workout, when he is usually joined by his personal trainer and physical therapist, Drew Contreras, if he doesn't ride his Peloton bike.

"If I let it go for a week, I feel it," he told the "Smartless" podcast recently. "I used to be able to go for a week and nothing would change."

White House aides say Biden reads his briefing book deep into the night, holds intensive evening meetings with advisers and has never balked at their scheduling requests that may have him out late, though rarely up early.

Yet his aides are deeply protective of the president, especially with his public schedule, which is lighter than those of Barack Obama and George W. Bush, both far younger in office. They've shielded him from formal interviews and, until recently, press conferences.

To his doubters, he says: "Watch me."

Biden has been diagnosed with several very common age-related health conditions, none causing him serious problems.

In his November 2021 summary of Biden's health after the president's first full physical in office, Dr. Kevin O'Connor noted Biden's gait had become somewhat stiffer, something doctors watch for in older patients as it could signal a fall risk.

But after testing, the doctor concluded it's mostly due to ongoing "wear and tear" arthritis of the spine, as well as compensation for a broken foot sustained a year earlier and the development of "mild peripheral neuropathy" or subtle damage to some sensory nerves in the feet.

Experts say age is not destiny; what matters is good health, fitness and functioning. Japanese climber Yuichiro Miura had enough of those attributes to make it to the top of Mount Everest in 2013 at age 80, setting a record that an 85-year-old Nepali man died trying to break in 2017.

Growing old is inexorable — at whatever pace, it comes.

It came at one pace for Supreme Court Justice Thurgood Marshall, for example, and it's coming at another for Pelosi, who is another institution in town.

"What's wrong with me?" Marshall asked upon his decision to retire from the Supreme Court at age 82, before answering: "I'm old. I'm getting old and coming apart." (He died two years later.)

At the same age, Pelosi buzzes Capitol hallways in high heels, outpacing much younger people. And her cognitive abilities have never been in question.

The knock against her was that she blocked the highest ambitions of generations of younger lawmakers before her decision this past week not to seek reelection as House Democratic leader when Republicans take control.

Supreme Court justices, shielded from the electorate and bosses, can grow as old in the job as they want and as fate allows — and they tend to stick around. Justice John Paul Stevens retired in 2010 at age 90, attributing his decision to a small stroke while reading his Citizens United dissent from the bench.

Ruth Bader Ginsberg, a hugely consequential 80-something, fell three years short of her goal to be as old as Stevens on the bench. She died in September 2020.

In democracies, where voters are the boss, and in autocracies, where they're not, plenty of people in power soldier on in their advanced years, even if few are up there like former Malaysian Prime Minister Mahathir Mohamad, who became the world's oldest leader at 92 and is running to get the office back, at 97.

Much of the leadership in the U.S. Congress is over 70, especially Democrats, and so were Biden's main rivals in the 2020 Democratic primaries and Trump.

Attribute that, in part, to increasing longevity.

"Life expectancy back around 1900 in the United States was about 50," Olshansky said, "and we added about 30 years" since.

In Cockeysville, Maryland, outside Baltimore, Nelson Hyman, 85, and his wife, Roz Hyman, 77, credit Biden with getting big things right and especially with appointing a strong team. To these Democrats, that adds up to an effective presidency that taps the value of age in a society that often doesn't.

"I've always felt the president is as good as the people that he appoints, and I think he's appointed some very, very good people, very competent people, and he uses them," said Roz, a retired counselor in a psychiatric hospital.

"Now, are you going to ask me, is he going to be competent in two years? Who knows? I don't know."

A president can only be conceptual, said Nelson, retired from an insurance career, "and the detail people will take care of the details." When Russia's Vladimir Putin invaded Ukraine, he said, Biden stepped up, "spoke beautifully and strongly" and "has not been afraid to deal with Putin. Not at all."

They recalled seeing Ronald Reagan struggle in his second term, before he was diagnosed with Alzheimer's after he left office, and felt that he, too, had surrounded himself with competence, as much as they disagreed with his direction.

Jamieson, director of the Annenberg Public Policy Center, said Reagan posted major achievements even when his memory may have been slipping, in part because his aides were strong and accomplished and Reagan retained the values that informed his judgments.

That's true of many presidents, Biden included, she said. Trump, in contrast, preferred a team largely of acolytes.

But when a perception does take hold in the public, any slipup can feed it, whether it is relevant or not.

When Biden tumbled on his bicycle in Delaware in June, his foot or feet caught in the pedals' cages, the mishap fed the perception of a president not at the top of his game physically.

"Those of us that know a little about aging were pretty impressed by the fact that he was on his bicycle to begin with ... that you've got somebody who is really active and healthy for his age," said Olshansky. Instead, the focus was on his injury-free fall.

Ageism pops up in campaigns even when opposing candidates are both old themselves; witness Trump's references to "Sleepy Joe" in 2020 and Biden's characterization of Trump as "mentally deranged."

But it was particularly pronounced in the 2008 presidential contest between Obama, 47 in that fall's campaign, and Sen. John McCain, then 72.

When Obama misidentified the city he was in, the flub was attributed to a long day by a nation-trotting barnstormer, Jamieson said. When McCain did that, it was his age.

The Obama campaign exploited the age gap in what Jamieson said were underhanded ways. She noticed and, with her technical team, confirmed that in at least two ads, "Out of Touch" and "Seven," video of McCain had been slowed down. She concluded that was an effort to prime voters' concerns about McCain's age.

But the sharpest cracks about age came from McCain himself.

"Good evening, my fellow Americans," he said on "Saturday Night Live." "I ask you, what should we be looking for in our next president? Certainly someone who is very, very, very old."

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Associated Press writers Mark Sherman and Lauran Neergaard contributed to this report.

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This story was first published on Nov. 20, 2022. It was updated on Nov. 22, 2022, to make clear that the 2008 Obama campaign was found to have slowed video, not sound, of Republican presidential opponent John McCain.