Can Biden be replaced as Democrat nominee? Who could replace him?

Knives are out for President Joe Biden after his poorly received performance in the first 2024 presidential debate against Donald Trump.

Democratic sources told the BBC of panic and confusion within the party and discussions about whether Mr Biden, 81, should step down.

The New York Times editorial board – the beating heart of the US liberal establishment – said Mr Biden was a “shadow” of his former self and should stand aside.

But could Mr Biden back out now? What would happen? And who could replace him?

The short answer is that unless he agrees to stand aside, it’s difficult and could get ugly.

Let’s run through the scenarios.

Yes, if – and it’s a big ‘if’ – Mr Biden decides to retire, it would be relatively straightforward to find another candidate.

The party’s nominee will officially be chosen at the Democratic National Convention (DNC) in Chicago from 19-22 August.

The Democrats are planning to nominate Mr Biden and Vice-President Kamala Harris virtually before the gathering to comply with a ballot certification deadline in Ohio.

There, a candidate must win support from the majority of “delegates” – party officials who formally choose the nominee. Delegates are assigned to candidates proportionally based on the results of each state’s primary election.

This year, Mr Biden won almost 99% of the nearly 4,000 delegates.

According to DNC rules, those delegates are “pledged” to support the incumbent president.

If Mr Biden willingly drops out, it could turn into a free-for-all.

Democrats would be left with an open convention where they would suggest potential nominees and continue voting until one receives the majority of delegate votes.

That could spark a frantic contest among Democrats vying for a shot at the nomination.

Mr Biden has so far given no indication that he would consider stepping aside.

But if decides to drop out of the race, “that opens up an entirely different can of worms”, political historian Leah Wright Rigueur told BBC News.

“I think that if he were to get replaced, part of the negotiation for him stepping down would be that he would get the final say in who replaces him,” she said.

This is an even less plausible scenario. And if he doesn’t want to go, this is where the process gets really tricky.

In the modern political era, a major national party has never tried a hostile takeover of the nomination and there is no evidence of any serious plan to do so now.

However, DNC regulations do have some loopholes that could, in theory, make it possible to push Mr Biden out.

The rules allow delegates to “in all good conscience reflect the sentiments of those who elected them”, meaning they could look to someone else.

“It could be an incredibly ugly scenario,” Ms Wright Rigueur said.

Experts told BBC News they doubt there would be a revolt among party delegates.

But the DNC can alter party rules at any point.

Ms Wright Rigueur pointed to 1968, when President Lyndon B Johnson decided not to run for reelection.

The party shifted from an open convention process, in which delegates could cast ballots for whomever they chose, to a bound process, where a delegate was attached to a candidate based on primary results.

“At any point in time, the rules committee can change the rules surrounding how you select a presidential nominee,” she said.

“Nothing is outside of the realm of possibility,” she added.

Even if Mr Biden were suddenly to exit the race, conservative groups have vowed to file lawsuits challenging the legality of any replacement Democrat’s eligibility for the ballot.

Vice-President Kamala Harris would automatically take Mr Biden’s place if he were to step down during his presidential term.

But the same rules do not apply if Mr Biden pulls out as a candidate for November’s election race, and there is no mechanism in place that would give the vice-president an upper hand at an open convention.

Instead, Ms Harris would have to win the majority of delegates, just like any other candidate.

As she is already on the Democratic ticket, Ms Harris could certainly be favoured. But her relatively low popularity among the American public might dull that advantage.

Her net disapproval is now lower than Mr Biden’s and Donald Trump’s, according to FiveThirtyEight.

Mr Biden did face challengers from within his party this election cycle, including Minnesota congressman Dean Phillips and writer Marianne Williamson.

But both were longshots and neither is likely to rise to the top of any shortlist.

There are some calls for California Governor Gavin Newsom, Michigan Governor Gretchen Whitmer or Pennsylvania Governor Josh Shapiro to ride to the rescue.

But none of those candidates has publicly declared any wish to supplant the incumbent.

The 25th Amendment of the Constitution allows the US vice-president and the majority of the cabinet to declare the president unable to perform the duties of office.

If invoked, power is transferred to the vice-president to serve as acting president.

This has never happened before.

But following Thursday’s debate, senior congressional Republicans called on Mr Biden’s cabinet to consider invoking this clause.

After the US Capitol riot in 2021, the Democratic-controlled House approved a resolution urging then-Vice President Mike Pence to invoke the 25th Amendment to oust Trump, but the move went nowhere.