REPUBLICAN allies of Donald Trump could launch a lawfare plot to try and block Kamala Harris from running for president, reports claim.
But any such attempt from a nervous GOP to force Biden to remain on the ballot would likely collapse, experts have said.
After Biden's unprecedented withdrawal from the election, he endorsed Vice President Harris for the official Democratic nominee.
Although not yet a done deal, Harris is by far the likeliest candidate to nab the nomination at the Democratic National Convention in August.
There are even reports that delegates in the party could hold a virtual meeting to select her before the Convention begins in Chicago on August 19.
Republicans, who may be unsettled by the new energy coming from Harris' campaign, could be cooking up a plan to try and stop her from running.
Allies of Trump told CNN conversations are ongoing about whether they can challenge his removal from the ballot in favour of Harris.
It is unclear exactly what such a plot would look like - or whether concrete plans are in place to make it happen.
They may try to argue that putting Harris on the ticket is undemocratic, since most of the delegates had voted for Biden and are now left with few options against a ticking clock, reports claim.
Other possible avenues include trying to remove her access to campaign funds or block her name from the ballot in certain states.
Harris already has the backing of at least 2,214 Democratic delegates, more than the 1,976 she would need in the first round of voting at the convention next month, by the Associated Press found.
Before Biden's official announcement, the most prominent Republican in the house - Mike Johnson - said in a CNN interview that there might be "legal hurdles" in certain US states when swapping candidates.
He also threatened to sue to try and force Biden, significantly behind Trump on the polls, to remain in the race - at least in some US states.
Johnson told ABC News: “Every state has its own system... and in some of these, it’s not possible to simply just switch out a candidate.”
But Elaine Kamarck, a member of the Democratic National Committee's rules committee, told USA Today she doesn't expect a serious Republican challenge against Harris.
Other legal experts have largely rubbished theories that those arguments would stand up in a court of law.
Justin Levitt, a political law professor at Loyola Law School told CNN that a challenge like that "misunderstands" the presidential primary process.
Biden was selected by delegates during the Democratic primaries.
But those delegates are not legally bound to officially nominate him at the convention if they do not want to - or if, in an extreme scenario like this - he is no longer standing.
They also don't have to vote for Harris simply because she is Biden's first choice, although it is largely expected.
Ben Ginsberg, a Republican campaign lawyer, said: "I find it impossible to believe a lawsuit like that would be successful."
He did warn: "But for the performative art of thinking that might somehow cast doubt on Harris’ legitimacy, it’s not impossible that somebody will file a non-meritorious suit to try and dust things up."
More challenges from the GOP could point to the serious funds raised by the Biden-Harris campaign before the President quit - some $240 million.
Harris has already filed the paperwork needed to show her as the new presidential candidate, and since she was already on the Democratic ticket, there is likely no legal basis for a challenge.
Not to mention she herself saw more than $81 million in donations in only 24 hours after the campaign kicked off.
Republicans in Trump's camp tried to use lawfare before in 2020 to overturn the election that saw Biden beat Trump to the White House - and failed.
There are also only around 100 days between now and the election on November 5.
Any legal complaints from the Republican camp could take months or even years to see through - and bureaucratic processes would stretch this even further.
There is also legal precedent to consider, previous court decisions made in the US which set out benchmarks for further legal cases.
Trump v Anderson, a Supreme Court case, looked at the attempt by Colorado to remove Trump from their state ballot because of his role in the January 6 Capitol riot.
It set out a standard that would prevent states from overruling either the Republican or Democratic party's choice of candidate.
If a plan is in the works from Trump's camp to challenge Harris - it is likely standing on shaky legs and won't hold up in a court of law.
President Biden has endorsed Vice President Kamala Harris but naming a new Democratic nominee won't be a simple process.
Here's what's next after Biden's stunning announcement.
Biden secured nearly 4,000 delegates by winning state caucuses and primaries earlier this year. He was set to officially be named the Democratic nominee at a virtual vote ahead of the Democratic National Convention, which begins on August 19.
However, Democratic party rules don't allow Biden to simply pass his 3,896 delegates to Harris or another candidate.
Harris will now have to convince those nearly 4,000 delegates and 700 superdelegates to support her and name her nominee.
Delegates are free agents who can choose to support whichever candidate they want - likely without input from voters at this stage since primaries and caucuses were already held.
All eyes are now on the previously planned virtual vote - where the Democratic party could choose a nominee before the DNC begins.
Biden's endorsement of Harris will likely sway delegates and no one has publicly challenged her as a candidate - but delegates are not required to back her.
Even if the virtual vote isn't held, the party could still choose Harris or another candidate before the convention.
If Democrats don't name their nominee before the DNC, it'll be the first open and contested convention since 1968.
