US President Joe Biden’s poor debate performance is raising questions about whether Democrats can field an alternative candidate if the 81-year-old leader leaves the race.
Moments after Thursday night's debate with Donald Trump ended, panicking Democrats declared the event to have been a disaster for Mr Biden, who appeared frail and frequently struggled to finish his sentences.
“That's a good man. He loves his country. He's doing the best that he can,” said Van Jones, a political analyst for CNN.
“But he had a test to meet tonight to restore confidence in the country and of the base, and he failed to do that.”
David Axelrod, a former campaign strategist for president Barack Obama, said Mr Biden did “get stronger as the debate went on but by that time, I think the panic had set in”.
“You’re going to hear discussions that I don’t know will lead to anything, but there are going to be discussions about whether he should continue.”
With Mr Biden having already secured the presumptive nomination, Democrats’ prospects for a course change are diminishing.
Here is a look at how a last-minute alternative to Mr Biden could emerge.
Is there a precedent?
President Lyndon Johnson decided not to seek nomination for a second full term in 1968, as Vietnam War protests mounted.
In an Oval Office speech, Mr Johnson made the surprise announcement: “I shall not seek, and I will not accept, the nomination of my party for another term as your president.”
But that was at the end of March – extremely late even before the nomination calendar became as front-loaded as it is today. Unlike Mr Johnson, Mr Biden has already secured enough delegates for the nomination.
Can Biden be removed from the ticket?
It would be difficult.
Mr Biden faced minimal opposition in his party’s primaries and has secured 99 per cent of the pledged delegates before the Democratic National Convention.
Those delegates will be chosen in large part for their loyalty to the President. Absent extraordinary circumstances – and a backup plan – it is unlikely they would remove him from the ticket.
Any challenger to Mr Biden would have to announce his or her candidacy before the formal vote, publicly challenging the incumbent in a high-stakes attempted party coup.
How soon must a decision be made?
The Democratic National Committee (DNC) on August 19 is when the party formally announces its presidential candidate pick.
Any effort to replace Mr Biden must be completed before then – unlikely given his determination to stay on the ballot.
But not all Democrats joined the chorus of concern.
“I refuse to join the Democratic vultures on Biden’s shoulder after the debate,” Senator John Fetterman wrote on X.
“No one knows more than me that a rough debate is not the sum total of the person and their record.”
What if Biden steps down after the convention?
The decision to replace him would be made by the members of the DNC. But then the party would face another hurdle: printed ballots with Mr Biden’s name already on them.
Laws vary by state about how a vote for Mr Biden would be counted if he is no longer the nominee, but his votes are likely to go to his replacement when the Electoral College meets.
Who are the possible successors?
Vice President Kamala Harris is the most logical heir apparent, but it would not be automatic.
Other candidates waiting in the wings – who deferred to Mr Biden and continue to publicly support him – include California Governor Gavin Newsom, Illinois Governor JB Pritzker and Michigan Governor Gretchen Whitmer.
None of those candidates have polled any better against convicted felon Trump than Mr Biden does, according to a Bloomberg News/Morning Consult poll of seven battleground states.
