How Trump’s nightmare could be president
Donald Trump likes to call her "Crazy Nancy", but there is a chance House Speaker Nancy Pelosi might have the last laugh.
Ms Pelosi, if she gets her way, could be crowned President Pelosi.
The process, known as a "contingent election", is outlined in the 12th Amendment to the US Constitution.
Normally to win a US Presidential election, a candidate must win enough states to reach 270 electoral college votes.
There are 538 electors representing the 50 states and the District of Columbia, meaning 270 is the "magic number".
If neither candidate reaches 270, the 12th Amendment stipulates that the Presidency is voted on by the House of Representatives, while the Senate decides the Vice Presidency.
It's only ever happened twice in America's history - in 1825 when the House voted to elect John Quincy Adams as President, and in 1837 when the Senate voted to elect Richard Mentor Johnson as Vice President.
In 2016, Mr Trump won 304 electoral college votes to Hillary Clinton's 227.
While Mr Biden is currently the clear favourite to unseat the Republican incumbent next month, opinion polling in 2016 was notoriously inaccurate.
Polling analysis website FiveThirtyEight currently puts the likelihood of Congress deciding the election if neither candidate reaches 270 electoral college votes at under 1 per cent.
But the University of Virginia's Center for Politics last month noted that if Mr Trump won every state currently listed as "toss-up", the result would be the "dreaded" 269-269 tie.
While that means it's a fairly unlikely scenario, it is 2020 after all - and both sides are taking the possibility very seriously.
Ms Pelosi last month began mobilising Democrats for the fight, Politico reported.
Crucially, a contingent election is different to a regular House vote in that each state delegation only gets one vote, as opposed to each member.
That means a state like Alaska, which has only one representative in the House, gets an equal say as more populous states like California and Texas, which have 53 and 36 respectively.
Which way each state delegation votes is based on a simple majority among the representatives.
As it stands, while Democrats hold the majority with 232-197 seats, Republicans actually control more overall state delegations.
Twenty-six state delegations currently have a Republican majority while 22 have a Democrat majority.
Pennsylvania is tied on nine-nine, while Michigan has seven Democrats, six Republicans and independent Justin Amash - who would be expected to vote with Democrats given he defected from the Republican Party.
But the vote would not be taken by the current Congress, but by the Congress elected on November 3.
The new Congress will be sworn in on January 3, and members convened to count electoral votes on January 6.
"The Constitution says that a candidate must receive a majority of the state delegations to win," Ms Pelosi said in a letter to House Democrats last month.
"We must achieve that majority of delegations or keep the Republicans from doing so."
She added that it was "sad we have top plan this way, but it's what we must do to ensure the election is not stolen".
Democrats are now aggressively targeting key seats that could flip entire state delegations, particularly in places like Montana and Alaska where they will get more bang for their buck.
While Mr Trump and Republican House candidates are still favoured to win those states, according to FiveThirtyEight, Democrats have grown increasingly competitive.
"We're trying to win every seat in America, but there are obviously some places where a congressional district is even more important than just getting the member into the US House of Representatives," Maryland Democrat Representative Jamie Raskin told Politico.
Mr Trump is also keenly aware of the issue.
Speaking to supporters at a rally in Pennsylvania last month, the President reiterated his claims that the election will be a "disaster" due to issues with mass mail-in voting, but nevertheless argued Republicans would have the advantage if the vote went to Congress.
"I don't want to end up in the Supreme Court and I don't want to go back to Congress either, even though we have an advantage if we go back to Congress," he said.
"Does everyone understand that? I think it's 26 to 22 or something, because it's counted as one vote per state. So we actually have an advantage."
The UVA's Center for Politics, for its part, predicts Republicans will have the edge in a contingent election scenario.
"Even though Democrats hold a House majority and remain on track to maintain that majority next year, Republicans actually have and are likely to maintain an edge in a possible electoral college tiebreaking vote," UVA's Kyle Kondik wrote.
But he questioned whether "in a world in which Republicans are losing a statewide House race in Alaska or Montana or Democrats are otherwise cutting into these GOP-controlled House delegations", the electoral college would be "knotted at 269-269".
"Probably not - in that world, Joe Biden is probably also winning the electoral college outright," he said.
Originally published as How Trump's nightmare could be president