US President Joe Biden has ended his re-election campaign after
and ability to beat Donald Trump, endorsing Vice President Kamala Harris to replace him as the party's candidate.
Biden, 81, in a post on X, said he will remain in his role as president and commander-in-chief until his term ends in January 2025 and will address the public this week.
"It has been the greatest honour of my life to serve as your President. And while it has been my intention to seek re-election, I believe it is in the best interest of my party and the country for me to stand down and to focus solely on fulfilling my duties as President for the remainder of my term," Biden wrote.
His initial statement had not included an endorsement of Harris but he followed up a few minutes later with a post including an expression of support.
His move could clear the way for Harris, 59, to run at the top of the ticket.
It was unclear whether other senior Democrats would challenge Harris for the party's nomination — she was widely seen as the pick for many party officials — or whether the party itself would choose to open the field for nominations.
Trump, the Republican candidate in the 5 November election, told CNN that he believed Harris would be easier to defeat.
Biden abruptly changed his mind about 2024 race over weekend
Biden had a change of heart on Sunday, a source familiar with the matter told Reuters news agency.
The president told allies that as of Saturday night he planned to stay in the race before changing his mind on Sunday afternoon.
"Last night the message was proceed with everything, full speed ahead," a source familiar with the matter told Reuters, speaking on condition of anonymity.
"At around 1.45pm today: the president told his senior team that he had changed his mind."
Biden's announcement follows a wave of public and private pressure from Democratic lawmakers and party officials to quit the race after
against Republican rival Trump, 78.
Days later he raised fresh concerns in an interview,
, and saying he would be fine losing to Trump if he knew he'd "gave it my all".
His
- invoking Russian President Vladimir Putin's name when he meant Ukrainian President Volodymyr Zelenskiy and calling Harris "Vice President Trump" — further stoked anxieties.
Only four days before Sunday's announcement,
, forcing him to cut short a campaign trip to Las Vegas.
Who could replace Biden in the Democratic ticket?
Several candidates could step into the fray.
Harris is at the top of the list, but she has had her own problems after a rocky start in the job and poor polling numbers. The US Constitution dictates that the vice president becomes president if the president dies or becomes incapacitated, but it does not weigh in on an inter-party process for choosing a nominee.
, Michigan Governor Gretchen Whitmer, Kentucky Governor Andy Beshear and Illinois Governor JB Pritzker have all been floated as possible replacements. Up until now they have been Biden supporters working to help get him elected.
How will a nominee be chosen?
There could be a free-for-all of sorts between the Democratic heavyweights vying for the job.
According to Ballotpedia, there are expected to be some 4,672 delegates in 2024, including 3,933 pledged delegates and 739 so-called superdelegates — senior party members.
In order to secure the nomination, a candidate would need to get a majority — that is, more votes than all the others combined.
If no one achieves that, then there would be a "brokered convention" in which the delegates act as free agents and negotiate with the party leadership.
Rules would be established and there would be roll call votes for names placed into nomination.
It could take several rounds of voting for someone to get a majority and become the nominee. The last brokered convention when Democrats failed to nominate a candidate on the first ballot was in 1952.
What happens to Biden's campaign cash?
The Biden-Harris campaign had $91 million in the bank at the end of May, but experts on campaign finance law disagree on how readily the money could change hands.
Because Harris is also on the campaign filing documents, many experts believe the money could be transferred over to her if she is on the ticket. But there is some debate about whether Biden would need to be officially nominated first as the party's candidate before a transfer could be made.
What led to Biden's decision to drop out?
Biden's historic move — the first sitting president to give up his party's nomination for re-election since President Lyndon Johnson in March 1968 — leaves his replacement with less than four months to wage a campaign.
Biden was the oldest US president ever elected when he beat Trump in 2020.
During that campaign, Biden described himself as a bridge to the next generation of Democratic leaders.
, a transitional figure who beat Trump and brought his party back to power.
But he set his sights on a second term in the belief that
amid questions about Harris' experience and popularity.
His team had hoped a strong performance at the 27 June debate would ease concerns over his age.
But donors began to revolt and supporters of Harris began to coalesce around her.
He held damage-control calls and meetings with lawmakers and state governors, and sat for rare television interviews.
Polls showed Trump's lead in key battleground states widening, and Democrats began to fear a wipe-out in the House and Senate.
On 17 July, California's Representative Adam Schiff called on him to exit the race.
Earlier this year, facing little opposition, Biden easily won the Democratic Party's primary race to pick its presidential candidate, despite voter concerns about his age.
