Joe Biden has succumbed to pressure to stand down as the Democratic presidential candidate – so how could he be replaced and how might it work?
A national US party has never tried to force an election candidate to step down in the modern era.
Consequently, we are in uncharted territory, with no clear guide as to what the Democrats will need to do in order to find an alternative presidential candidate.
The voting in the state primaries confirmed Mr Biden as the pick for November’s election.
The 81-year-old won nearly all delegates and he was due to be confirmed as the candidate at the Democratic National Convention in late August.
Biden will now serve out the rest of his presidency and stay in the White House until the incoming leader takes over in January.
But the Democrats will have to come up with a replacement in the coming weeks.
But how will his replacement be chosen?
There will likely now be a frenzy among Democrats as there’s no protocol to choose a new candidate before the convention which starts on 19 August.
It takes a majority of the party’s 4,000 or so delegates to win the nomination – and Mr Biden secured about 3,900 in the primaries.
As leader of the party, he may have some influence over the process – and has already given his support for his vice president Kamala Harris – but it could become a ‘free for all’ with candidates campaigning aggressively to win their vote at the convention.
The party will be extremely keen to avoid scenes of infighting months out from the election – however, it could prove unavoidable.
What is not clear is whether the Democrats will wait until the convention to put those in the frame on show or whether they will work out some way of ensuring the potential nominee is decided before the convention so delegates rally round the chosen pick.
Could Kamala Harris become the new pick?
The vice president was touted as the favourite if Mr Biden ditched his re-election bid, and he has now thrown his support behind her.
However, his delegates will not transfer to her automatically and she will have to compete for their vote with any other hopefuls that come forward.
Recent polls suggest she would fare about the same as Mr Biden in the election, but still ultimately lose to Trump.
Read more about her here.
Who else could enter the race?
Two names frequently mentioned were California governor Gavin Newsom, 56, and Michigan governor Gretchen Whitmer.
They didn’t enter this year’s primaries but have both been talked about as potential presidential nominees in future.
Mr Newsom has tweeted since Mr Biden’s announcement, praised the president but gave no indication as to whether he would stand or not.
Read more:
As Joe Biden steps aside, who will replace him?
Ms Whitmer, a lawyer and former prosecutor, was the Senate’s first female Democratic leader and became governor in 2018.
The 52-year-old also served as co-chair of Joe Biden’s 2020 election campaign.
She has also tweeted since Mr Biden’s announcement and was non-committal, giving her support to the process, rather than any one person.
But with Mr Trump ahead slightly in the polls, could the pair be convinced to go ahead? And will anyone else throw their hat in the ring.
Others mentioned as potential nominees include Kentucky governor Andy Beshear and Illinois governor JB Pritzker
Interestingly, former first lady Michelle Obama – seen as a long shot this time around – would beat Trump and outperform Mr Biden, Mrs Harris and all the other likely replacements, according to a recent Reuters poll.