By Sarah Smith, BBC North America editor
Many Democrats are rapidly coalescing around Kamala Harris as their new candidate. Photo: AFP / Jeff Kowalsky
Analysis: It's just over a week since Donald Trump was almost assassinated at a rally in Pennsylvania. And in the last eight days the US presidential election has been totally turned on its head.
In that short time Trump has been greeted like a messiah at the Republican National Convention and crowned as the party's candidate, whilst Joe Biden has been reluctantly forced out of the race.
Obviously it was Biden's disastrous performance in the televised debate last month that caused the panic within the Democratic Party - but their doubts went deeper than that.
The president was trailing Trump in the polls before he challenged his opponent to a live televised debate.
He only came up with that idea because he urgently needed to reset his campaign.
The hope was that getting voters to focus on what Trump could do if he was re-elected to the White House would boost support for Biden. His campaign was based around the idea that if this election was a referendum on Trump then Biden would win.
But the rambling and incoherent performance from the president immediately turned this into a referendum on Biden and his fitness for office.
Suddenly it was an open secret that the president had episodes in which he was far from cogent. The excuses - he had a cold, he had jet-lag - were weak and scarcely believable.
Savvy Democrats also sensed a potential opportunity. A chance to transform this race and maybe energise voters who were seriously disenchanted with having to make a choice between the same two old men who ran against each other last time.
Any contest to select a new candidate will have to be brief. The Democratic National Convention is scheduled to confirm its candidate on 19 August.
But four weeks of debates, hustings and town hall events with some of the party's talented and experienced younger candidates could be exciting and attract the attention a new nominee will need.
Yet it seems that the party is rapidly coalescing around Vice-President Kamala Harris as their new candidate.
Signs outside a US Naval Observatory where US Vice President Kamala Harris lives, in Washington, DC on 21 July, 2024, after Joe Biden announced he would step aside from the 2024 presidential race. Photo: AFP/ Daniel Slim
So many elected representatives, senators and party grandees are backing her that she may be unassailable.
None of the serious contenders who could have challenged her - California Governor Gavin Newson, Michigan Governor Gretchen Witmer or Pennsylvania Governor Josh Shapiro are going to put up a fight. As they say in American sports, "the fix is in".
Democrats have just watched the Republican Party unite around the cult of Donald Trump. Republicans don't just support their nominee, they adore him.
Former US president and 2024 Republican presidential candidate Donald Trump accepts his party's nomination on the last day of the 2024 Republican National Convention, on 18 July. Photo: AFP / Angela Weiss
The prospect of contrasting Trump's triumphant coronation as his party's candidate with a scrappy fight for the Democratic nomination may seem too risky - even if large sections of the party are less than enthusiastic about Harris.
One Democratic operative told me, a few days before Joe Biden stood down, that Harris was nothing more than "an empty suit who has neither an ideological rudder or a moral compass". But they said they'd get behind her if that's what it took to get Biden off the ballot.
The biggest battle may be over who Harris picks as her running mate.
Among the issues to be decided - who will be Kamala Harris's running mate. Photo: Andrew Harnik / Getty Images / AFP
The key challenge will be to attract the attention of voters in a contest in which they are running against a former president who constantly manages to consume all the oxygen in this election.
"Never let a serious crisis go to waste" is a favourite quote from Barack Obama's chief of staff Rahm Emanuel - although he may have borrowed it from Churchill.
What he meant was that a crisis can be an opportunity to do things you could not do before. The Democrats have seized the crisis caused by Biden's debate performance and used to it to transform the coming election.
It was Biden himself who said that the result of this election would be crucial in determining the future of American democracy. Democrats contend that Donald Trump poses an existential threat to the nation's democratic institutions.
In these circumstances they have to do anything they can to find a winning candidate. The situation had become dire enough that they forced a sitting president to step aside. But they may not be bold enough to allow an open contest to find the best candidate to replace him.
- This story was first published by the BBC
