Despite weeks of crisis talks and dozens of Democrats calling for him to step down, Joe Biden’s decision to withdraw was made at the last minute.

The 81-year-old president was isolating with COVID at his $3.4 million holiday home in Rehoboth Beach, Delaware, when his shrinking inner circle handed him polling data showing he could no longer beat Donald Trump.

That was when they composed a letter saying it was time for him to step aside for the good of the future of the Democratic party.

Donors had pulled millions of dollars in funds, the list of Democrats telling him to drop out was growing by the day, and polls suggested that his chances of beating Donald Trump were dwindling after his disastrous debate performance.

Jill Biden was there when her husband eventually made the historic call, giving into mounting pressure. But a spokeswoman for the First Lady said it was the president's judgment alone, and confirmed he made it late.

'Down to the last hours of the decision only he could make, she (Jill Biden) was supportive of whatever road he chose,' the spokeswoman said. 'She’s his biggest believer, champion, and always on his side, in that trusted way only a spouse of almost 50 years can be.' 

The question now is what pushed Biden to finally make the extraordinary move that blindsided some of his White House staff and most of the people working on his re-election campaign.

On Saturday evening, Biden summoned to his side two men who have been there since his political start: advisers Steve Ricchetti and Mike Donilon. They have been with him through the best of times - his first years as a senator - and the worst of times - the death of his son Beau Biden in 2015.

Already with the president and the first lady were their closest aides Annie Tomasini and Anthony Bernal, who they refer to as 'family.'

It was Ricchetti and Donilon who brought with them devastating new data which would help to make up Biden's mind.

They revealed the latest internal campaign polling, taken since the debate, which showed he could no longer beat Trump.

Biden's decision was made soon after, and he asked Ricchetti and Donilon to start drafting a letter, and to begin the process of how to make a public announcement, DailyMail.com confirmed. The president also began telling his family.

Biden had previously insisted that he would only step aside if he was shown polling that proved Kamala Harris would fare better than him against Trump, or if he developed a 'medical condition'. In the end, it was the first of those developments that sealed his fate.

Biden went to bed on Saturday night at the beach house, knowing he would announce his bombshell the next day.

At 1:45 pm on Sunday he began calling his senior staff at the White House and the campaign.

By that time he had already told Harris and Senate Majority Leader Chuck Schumer. 

At 1:46 pm, his campaign account posted a letter from the president announcing his decision even as he was still on the staff call.

Most of his staff – both in the White House and at the campaign - were shocked. They learned the news online, getting the alert when the @JoeBiden account posted the president's missive.

'No one had a heads up before the tweet posted,' a campaign staffer told DailyMail.com. 'Which, to me, is an insane way to treat the 1300 people that work for you on the campaign.'

It capped a chaotic 48 hours for the Biden family as they hunkered in behind their patriarch with a small, inner circle of longtime aides supporting them. Some were even reporting back to Jill Biden about those staffers deemed disloyal.

Meanwhile, Biden had veered from angry at the pressure from his party to acceptance of the situation.

And once his final decision was made on Saturday night, the rest moved quickly. 

Biden called Harris directly to tell her the news.

He also had one-on-one calls with White House chief of staff Jeff Zients and campaign chair Jen O'Malley Dillon, according to reports. He would also speak with his Cabinet, Members of Congress, governors, and supporters.

But it all happened so fast many staff were hurt about the way they learned of the news, although they weren't surprised by it. 

The writing has been on the wall. Almost 40 Democratic lawmakers had called on Biden to exit the race. Major donors were threatening to pull their support. Actor George Clooney wrote an op-ed in the New York Times calling on Biden to step down. And Barack Obama was reportedly working behind the scenes to get Biden to move aside.

It 'needed to happen,' a Democratic aide said. 'But he kinda just dropped a bomb. Like it's not surprising but it's shocking.'

Another staffer said people were feeling 'a mix of relief, gratefulness, hope.'

The campaign held an all-hands on deck call at 5 pm ET to reassure staff they still had their jobs.

Campaign Chair Jen O'Malley Dillon acknowledged that it was 'hard for staff who may have gotten the news while they were working or door knocking, but it was important for the president to hear from him in his own words.'

Publicly, aides have been loyal to Biden. 

Many have gone on TV and taken to social media to defend the president since his disastrous debate performance against Donald Trump 24 days ago, arguing Biden was the party's nominee and planned to stay the nominee.

Since the June 26th debate, staff had been trying to go about business as usual, pushing back at reports Biden would drop out.

'Fanfiction' declared deputy press secretary Andrew Bates said of reports Biden would drop out this weekend, advising Democrats to 'keep the faith.'

Even on Sunday morning, the message from the campaign was Biden was in it to win it. 

Campaign co-chairman Cedric Richmond, said on CBS Face the Nation on Sunday morning: 'I want to be crystal clear. He's made a decision and that decision is to accept the nomination and run for reelection, win reelection.'

Officials defended the manner in which the decision was announced.

It was made at the 'last minute,' a White House official said.

It was actually made in the last 24 hours, with only Biden's family and a small circle of close aides knowing of his decision.

And by withholding it from senior staff until the last minute - and not telling junior staff at all - the news didn't leak. It came out on Biden's terms.

It all fits with a man said to be frustrated at what he saw as a public pressure campaign to force his hand.

Biden has spent the past four days being isolated both physically and politically.

He is at the beach house in Delaware, on the Atlantic Ocean as he recovers from COVID, still coughing and hoarse from the virus. First lady Jill Biden has been with him, although staying in a separate room.

And, it has been from there the president has watched Democrat after Democrat call for his exit even as he spent the past three weeks trying to reassure the party he was mentally and physically up to a second term.

But, despite everything he's done - national TV interviews, local radio interviews, a press conference, and campaign stops - nothing had quelled the tide against him.

In the aftermath of the decision, Biden's family was loud and clear in their love and support, praising him for his service to the country.

Jill Biden sent him her love on Sunday afternoon, retweeting his letter with two red hearts.

Naomi Biden, the Bidens' eldest granddaughter, wrote a long post on X, where she said she was 'proud' of her 'pop,' which is what the grandchildren call President Biden. 

She noted: 'Our world is better today in so many ways thanks to him. To the Americans who have always had his back, keep the faith. He will always have ours.'

And Hunter Biden said in a statement of his father: 'He is unique in public life today, in that there is no distance between Joe Biden the man and Joe Biden the public servant of the last 54 years. I'm so lucky every night I get to tell him I love him, and to thank him. I ask all Americans to join me tonight in doing the same. 

Thank you, Mr. President. I love you, Dad.'