WASHINGTON — The people closest to President Joe Biden were well aware that he had changed. He talked more slowly than he had just a few years before, needed to hoist himself out of his seat in the presidential limousine and walked with a halting gait.

"Your biggest issue is the perception of age," Mike Donilon, the president's longtime strategist, told him in mid-2022, according to three close aides who heard it. That bit of feedback, delivered repeatedly by Donilon, was the sort of blunt talk that did not often make its way to a man who had spent a half-century in politics prizing loyalty and deference.

Biden acknowledged the concerns, but the warnings only ignited his defiant, competitive streak. In April 2023, without convening his family or having long deliberations with aides, he announced he was running again.

Now, as President-elect Donald Trump heads back to the White House, demoralized Democrats debate what might have been had the president bowed out in time to let a younger generation run. Biden, 82, has at the same time made the extraordinary admission that he might not have made it through a second term. "Who knows what I'm going to be when I'm 86 years old?" he said in an interview with USA Today on Jan. 5.

The president's acknowledgment has put a new spotlight on his family and inner circle, all of whom dismissed concerns from voters and Biden's own party that he was too old for the job. And yet they recognized his physical frailty to a greater degree than they have publicly acknowledged. Then they cooperated, according to interviews with more than two dozen aides, allies, lawmakers and donors, to manage his decline.

They rearranged meetings to make sure Biden was in a better mood — a strategy one person close to him described as how aides should handle any president. At times, they delayed sharing information with him, including negative polling data, as they debated the best way to frame it. They surrounded him with aides when he walked from the White House to the waiting presidential helicopter on the South Lawn so that news cameras could not capture his awkward bearing.

They had Biden use a teleprompter for even small fundraisers in private homes, alarming donors, who were asked to provide questions beforehand. They came up with replacing the grand steps that presidents use to board Air Force One with a shorter set that led directly into the belly of the plane. They chastised White House correspondents for coverage of the president's age. They hand-delivered memos to Biden describing social media posts the campaign staff had persuaded allies to write that pushed back on negative articles and polls.

Biden's fumbles continued this week. In announcing a ceasefire deal between Israel and Hamas on Wednesday, he confused the emir of Kuwait with the emir of Qatar and said Hezbollah rather than Hamas was responsible for the Oct. 7, 2023, attack on Israel. He also referred to his national security adviser as "Secretary Jake Sullivan" before catching himself.

Six key people protected the president.

Jill Biden, the first lady, and Hunter Biden, his eldest son, fervently believed in his ability to win. Donilon and Steve Ricchetti, the counselor to Biden, knew when and how to deliver information, along with Annie Tomasini, the deputy chief of staff. She and Anthony Bernal, the first lady's most senior aide, took tight control over the president's public schedule.

All of them are deeply devoted to Biden. All are adept at navigating his quick temper. All enjoy proximity to the most powerful office in American politics.

And all were convinced that he was the only one who could beat Trump.

Then there was Biden himself, whose pursuit of the White House had been the family's project for nearly 40 years. Finally elected on his third try, Biden suggested that he would be a transition president. But his pride, plus a string of legislative accomplishments and a strong showing in the 2022 midterms, drove him to seek reelection and set out on a quixotic mission to prove his vitality.

Biden told USA Today that he could have defeated Trump if he had stayed in the race. But when he departs the White House on Monday, history will remember him as the man who beat Trump, then paved the way for his return.

The final campaign begins

Biden's announcement in the spring of 2019 that he was running against the incumbent Trump came after meetings with family members to prepare them for the scrutiny. It was a difficult time. Biden's son Beau had died of brain cancer in 2015, and the other, Hunter, had collapsed into addiction and financial ruin. Biden had to assume a bigger role in financially and emotionally supporting his grandchildren.

There were no such meetings when he considered a final run. His surviving son was sober. His grandchildren were better off. He could do it.

But the concerns over his age were there from the start.

In May 2023, a month after he had announced he was running for reelection, Biden was in the Fifth Avenue duplex of Hamilton E. James, the billionaire former president of Blackstone, making his case about another term to nervous New York donors.

"It wasn't an automatic decision about running again," Biden, then 81, told the group, adding that he knew the road ahead would be relentless and brutal. "I thought to myself, four more years means six more years. It's a long time."

His comments, dropped into a 35-minute stump speech that meandered from Ukraine to his childhood, were meant to reassure. But to some donors, the comments had the opposite effect. Several left with the same worries over Biden's age that they had when they arrived. They told one another afterward that he hardly sounded like an energized, motivated candidate.

The president made so many rambling remarks at other fundraisers over the summer that several supporters called his advisers to plead for him to be more focused and on message. Others who saw Biden thought the wear and tear of the presidency was taking its toll.

"He looked a little tired," said Mark Gilbert, a longtime Democratic donor and a former ambassador to New Zealand. Gilbert held a fundraiser in Park City, Utah, for Biden in August of that year — in part, he said, for other donors who "wanted to see him in person, because they had read stories about how he'd lost a step." But Gilbert said the president had been "terrific" at the event.

Other interactions with donors were less rosy.

At a meeting with potential donors in Boston in the summer of 2022, the first lady heard directly from Joshua Bekenstein, the chair of Bain Capital. In an episode reported earlier by NBC, Bekenstein praised Biden's leadership, and said he could leave public life proud of a one-term legacy.

What happened next is not widely known. Bekenstein went on to say that if Biden was not running again, he should announce it to give other Democrats time to get in the race, according to two people briefed on the conversation. Bekenstein had been under the impression that Biden had promised to be a one-term candidate.

The first lady listened but did not reply. The meeting ended. Over time, Bekenstein was told how his comments had shocked administration officials who had been in the room.

Managing for stumbles

As several of Biden's current and former advisers tell it, guarding against criticism of his age was the obvious thing to do. So age came up often in political discussions weighing his perceived strengths and weaknesses as a candidate, often held with the president and the first lady in the White House residence. The consensus was that Biden might look old, but he was not too old for the presidency.

But at times, people familiar with his thinking recalled, Biden's pride — along with an old-school view that displaying physical vitality was the antidote to age concerns — could get in the way. Biden, who exercised on a stationary bike most days, made decisions that he thought would showcase vigor. But, at times, they had the unintended effect of showcasing his advancing years.

After fracturing his foot while playing with one of his German shepherds shortly before his inauguration, Biden refused to wear an orthopedic boot. He did not want to be seen as weak — a 78-year-old president with his hand on the Bible and a large, telltale contraption on his foot. He wore his leather brogues instead.

The end result, his friends and advisers say, was a fracture that did not heal, contributing to a shuffling gait that has continued through his presidency.

Biden still wanted to prove that he was physically agile. He enjoyed biking at his home near Rehoboth Beach, Delaware, but during the summer of 2022, when he stopped to talk with a group of onlookers and reporters, his feet got caught in the toe cages on the pedals. The president fell over, still attached to the bike.

Within days, critics turned Biden's fall into a political attack on T-shirts: "Running the country is like riding a bike."

The worst mishap was in June 2023, when Biden tripped over a sandbag at the Air Force Academy commencement. It took five seconds for Secret Service agents to help the president to his feet, an eternity when seen on television.

The sandbag was clearly in Biden's way, and anyone could have tripped over it. But the president's inner circle was alarmed. Their view was that the political damage could be catastrophic if he had one more fall like that, accident or not.

A grueling year of 'bad days'

Biden had pursued a final term in part because he felt his family was in shape to withstand an exhausting campaign. But by the time the race was underway, Hunter Biden's legal problems were mounting, and federal prosecutors were investigating the president for his handling of classified documents.

Special counsel Robert Hur ultimately concluded there was insufficient evidence to charge the president, but described him in a devastating report as a "well-meaning, elderly man with a poor memory." A transcript of Biden's five hours of interviews with investigators released a month later showed that he occasionally fumbled dates and the sequence of events but at most other points appeared clearheaded.

Still, the damage was done. It had not helped that Biden, furious about Hur's report, had stormed to the White House lectern to say he was up for the job — and then confused the presidents of Mexico and Egypt in response to a question about hostages held by Hamas.

Biden was struggling at the same time to manage support amid the stalemate in Ukraine and growing furor in his party over his support for Israel as its war in the Gaza Strip continued. The demands of foreign policy, several people familiar with his thinking said, consumed his time, attention and energy. Democrats had lost the House in the midterms. Pessimism about the economy was pervasive.

Taken together, those factors affected how Biden was scheduled and took a toll on his energy levels as he campaigned, people close to him said. He remained focused and in command in internal meetings, aides said. But, according to some, they also took to telling one another when it was a "bad day" — meaning that Biden's mood led to some meetings or calls being reshuffled to a better time. Other officials said it was because Biden was busy.

"The presidency is a real-time job, and President Biden determines his busy schedule and briefings based on the urgent needs of the country," Andrew Bates, a White House spokesperson, said Friday after this article was published.

Yet Biden pushed his staff to keep him scheduled and busy. As a result, he would at times seem tired and listless, particularly during or after overseas travel. His shaky condition was evident to foreign dignitaries during a trip to Normandy, France, in June for the commemoration of D-Day.

People who were there said he appeared disoriented at events and at times gazed off into the distance. At a state dinner at the Élysée Palace hosted by President Emmanuel Macron of France, a member of the French presidential staff approached an American attendee and asked with concern about Biden's health, saying he appeared "dans les vaps" — French slang for "out of it" or "in a fog." The trip occurred at the same time as Hunter Biden's trial on a gun charge in Delaware.

Two people involved in planning the president's schedule believe that in hindsight, he should not have been traveling so much during this period. He was exhausted from not one but two trips to Europe and a fundraiser in California in the weeks before his debate with Trump on June 27.

Biden needed naps during the debate preparations and then turned in a halting, incoherent performance universally described as "disastrous" by panicking Democrats. Even close aides aware of the president's frailties were stunned by what they saw. It was, as Sen. Chuck Schumer of New York recounted in a recent interview, "a big shock."

Three weeks later Biden dropped out of the race.

Still defiant, with days left in office

A drive to defy the odds is at the center of the Biden family. It was true when Biden won a long-shot race for a Delaware Senate seat against an older incumbent in 1972. It was true when he was counted out during the 2020 presidential primaries until a decisive Super Tuesday win in South Carolina changed his fortunes.

The key to survival was, and always has been, to buckle down and hang on. To keep the faith, as Biden would say.

He will never know what shape he would be in as an 86-year-old, two-term president. His advisers say that if anyone had sensed an opportunity to beat Biden — the only Democrat who has defeated Trump — they would have mounted a primary threat when there was still time.

The first lady, who married into the family in 1977, believes he would have been fine with a second term.

"I mean, today, I think he has a full schedule," Jill Biden said in an interview with the Washington Post that published Wednesday. "He started early with interviews and briefings, and it just keeps going."

Joe Biden's allies said he remained sharp in private situations.

Roger Harrison, who was Biden's deputy chief of staff when he was a senator in the 1970s and has remained a close friend, visited him at the White House in September, shortly after he had dropped out of the race.

"I'm sitting at the desk with him," Harrison recalled. "His staff brought in a speech on gun violence that he was going to deliver in the East Room that afternoon. So he goes through the speech, and he has a pen, and he goes line by line, page by page, marking it up. We then went to a meeting with his staff, and he told them what changes he wanted to make. It was like I was back in the Senate, when I would hand him a speech. His procedure was no different than what I saw 30 years ago, 40 years ago."

At the same time, Harrison said, he noticed "cosmetic changes" in how the president walked and spoke.

"I used to tell him, 'You know, you have a great voice. It's smooth. It's clear. You have a voice like Ronald Reagan. That's one of your attributes,'" Harrison said. "Sadly, it's noticeably less. But you know the old adage: Don't judge a book by its cover."

Doug Mills contributed reporting.