After weeks of relentless pressure, US President Joe Biden has ended his re-election campaign and endorsed Vice President Kamala Harris as the Democrat presidential nominee.

But it will be individual delegates who select the nominee, either in a virtual roll call tentatively scheduled for early August, or on the convention floor in Chicago next month, CNN reports.

Biden, whose political career spans more than 50 years, made his announcement in a letter posted on X, and followed up minutes later with a post endorsing Harris.

“Democrats  — it’s time to come together and beat Trump. Let’s do this,” he said.

In the earlier letter, Biden 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.

Former president and Republican challenger Donald Trump swiftly posted a searing assessment of Biden on social media platform Truth Social, saying “Crooked Joe Biden” was not fit to run for the office.

In a phone call with CNN minutes after Biden’s announcement, Trump said he thought Harris would be easier to beat than Biden would have been.

By dropping his re-election bid, Biden clears the way for Harris to run at the top of the Democrat ticket.

It is unclear whether other senior Democrats will challenge Harris for the party’s nomination – she was widely seen as the pick for many party officials – or whether the party itself will choose to open the field for nominations.

Biden had, reportedly, planned to stay in the 2024 presidential race as late as Saturday night (US time). But he told senior staff on Sunday afternoon that he was withdrawing, a source familiar with the matter told Reuters.

“Last night the message was proceed with everything, full speed ahead,” the source said, speaking on condition of anonymity.

“At around 1.45pm today, the President told his senior team that he had changed his mind.”

Former presidents salute Biden

After Biden’s announcement, Barack Obama said he was “one of America’s most consequential presidents, as well as a dear friend and partner to me”, and “a patriot of the highest order.”

Bill and Hillary Clinton praised Biden’s “extraordinary career of service” and said they were honoured to join him endorsing Harris, saying they would do whatever they could to support her.

Biden’s announcement follows a wave of public and private pressure from Democratic lawmakers and party officials to quit the race after his poor performance in a June 27 televised debate against Trump, 78.

Days later he raised fresh concerns in an interview, shrugging off Democrats’ worries and a widening gap in opinion polls, and saying he would be fine losing to Trump if he knew he’d “gave it my all”.

His gaffes at a NATO summit – invoking Russian President Vladimir Putin’s name when he meant Ukrainian President Volodymyr Zelensky and calling Harris “Vice President Trump” – further stoked anxieties.

Only four days before Sunday’s announcement, Biden was diagnosed with Covid-19 for a third time, forcing him to cut short a campaign trip to Las Vegas.

More than one in 10 congressional Democrats had called publicly for him to quit the race.

Biden is the first sitting president to give up his party’s nomination for re-election since Lyndon Johnson in March 1968. His historic decision leaves his replacement with less than four months to wage a campaign.

Biden was the oldest US president elected when he beat Trump in 2020.

During that campaign, Biden described himself as a bridge to the next generation of Democratic leaders.

Some interpreted that to mean he would serve one term, 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 he was the only Democrat who could beat Trump again amid questions about Harris’ experience and popularity.

His team had hoped a strong performance at the June 27 debate would ease concerns over his age. But donors began to revolt and supporters began to coalesce around Harris.

Top Democrats, including former House of Representatives Speaker Nancy Pelosi, a long-time ally, told Biden he cannot win the election.

Biden initially resisted pressure to step aside. He held damage-control calls and meetings with lawmakers and state governors, and sat for rare television interviews.

But it was not enough.

Polls showed Trump’s lead in key battleground states widening, and Democrats began to fear a wipeout in the House and Senate.

On July 17, California’s Representative Adam Schiff called on him to exit the race.

Biden’s departure sets up a stark contrast, between the Democrats’ presumptive new nominee Harris, a former prosecutor, and Trump who at 78 is two decades her senior and faces two outstanding criminal prosecutions related to his attempts to overturn the 2020 election result.

He is due to be sentenced in New York in September on a conviction for trying to cover up a hush-money payment to a porn star.

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.

 

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Who could replace Biden?

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

California governor Gavin Newsom, Michigan governor Gretchen Whitmer, Kentucky governor Andy Beshear and Illinois governor JB Pritzker have all been floated as possible replacements. Until now they have been Biden supporters working to help get him elected

How will they 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 4672 delegates in 2024, including 3933 pledged delegates and 739 so-called superdelegates – senior party members

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

Getting a majority could take several rounds of voting. The last brokered convention when Democrats failed to nominate a candidate on the first ballot was in 1952

-with AAP