US President Donald Trump and his campaign have already started to lay the groundwork to challenge or alter the results of the election should he lose to Joe Biden.

Mr Trump has aggressively pushed his case that states should announce a winner on November 3, election day, even though counting ballots could take weeks longer than normal.

His campaign has also repeatedly refused to rule out lobbying Republican-controlled state legislatures to switch their electoral college votes to Mr Trump, even if most voters cast their ballots for Mr Biden.

His insistence that states announce a winner on election night could mean a legal attempt to stop states from counting some mail-in ballots.

“It would be very, very proper and very nice if a winner were declared on November 3 instead of counting ballots for two weeks, which is totally inappropriate,” Mr Trump said on Tuesday.

“And I don’t believe that’s by our laws.”

White House spokeswoman Kayleigh McEnany has pushed the same line for weeks.

Mr Trump’s comments came the day after Justice Brett Kavanaugh, who he appointed to the Supreme Court, issued a similar opinion while defending the court’s ruling to stop Wisconsin counting ballots that arrived after November 3.

“Those states want to avoid the chaos and suspicions of impropriety that can ensue if thousands of absentee ballots flow in after election day and potentially flip the results of an election,” Mr Kavanaugh wrote.

“And those states also want to be able to definitely announce the results of the election on election night, or as soon as possible thereafter.”

The Trump administration removed mail sorting machines and mailboxes across the country in the months leading up to the election, worsening delays within the US postal system as voters seek to mail in their ballots.

John Hudak, deputy director at the Brookings Institution’s Centre for Effective Public Management, said Mr Kavanaugh’s “ignorant, error-filled” opinion does not “necessarily reflect the direction of the Supreme Court on issues like this".

“No state finishes counting ballots on election night. Not one,” Mr Hudak told The National.

“This is a desperate attempt by the president to sow doubt about what the outcome of an election is, and I think there are limits to what the Supreme Court and other federal courts are willing to tolerate.”

The Supreme Court has decided the fate of an election before.

In the US, the winner of the national popular vote does not necessarily win the presidency because of the electoral college system.

Each state has a certain number of “electors” based on population. These typically choose the next US president based on whichever candidate won the plurality of their state’s popular vote.

Florida in 2000 was a headache and a nightmare in a lot of ways, now imagine five or six Floridas all at once

John Hudak

Mr Kavanaugh’s opinion this week specifically cited the Supreme Court’s 2000 decision in Bush v Gore that prevented the key swing state of Florida from recounting ballots that the state’s voting machines had missed.

That paved the way for President George W Bush’s electoral college victory despite losing the popular vote.

Mr Kavanaugh, Chief Justice John Roberts and Amy Coney Barrett, who became Mr Trump’s third appointee to the court on Monday, all worked on Mr Bush’s 2000 legal team in Florida.

“Florida in 2000 was a headache and a nightmare in a lot of ways. Now imagine five or six Floridas all at once,” Mr Hudak said.

He said this was the most likely worst-case scenario, and it could occur if a candidate holds only a narrow lead in any of the key swing states.

The Trump campaign has also floated the idea of convincing Republican-held legislatures in swing states to flip the state’s electoral college votes in favour of the president if Mr Biden wins the state’s popular vote.

This month The Atlantic reported that Pennsylvania Republicans have discussed such a gambit with the Trump campaign.

While Mr Trump’s false claims that mail-in voting results in significant voter fraud would serve as the pretext for such a move, Pennsylvania’s Democratic governor would probably block such efforts.

But several battleground states with considerable clout in the electoral college have a Republican-held state legislature and a Republican governor, making such a move possible, even if legally dubious.

Those states are Florida, Texas, Ohio, Georgia and Arizona.

The Trump campaign did not respond to The National’s request for comment on this option.

“There will be Republican legislators happy to behave in anti-Democratic way,” Mr Hudak said.

But he said it was unlikely that any state legislature would muster enough votes to undo the will of the state’s voters.

“You have to assume there is a conscience at least in some but also a recognition that if we do this now, what will stop Democrats from doing this to us later,” Mr Hudak said.

Mr Biden’s supporters are more likely to vote by mail and Mr Trump’s supporters are more likely to show up to vote in person.

Because of this, some analysts have warned of a “red mirage”, where early results would initially indicate a victory for the president on election night, only to have Mr Biden win a state’s popular vote in later weeks as mail-in ballots are counted.

Americans, particularly Democratic voters, have already smashed early voting records and relied heavily on mail-in ballots.

While 22 states and the District of Columbia accept ballots that arrive after election day, as long as they are postmarked on or before November 3, at least six battleground states will not accept late ballots.

But swing states such as Florida, Arizona, North Carolina and Colorado can start counting mail-in ballots early.

Ohio, another key battleground state, leaves this up to the discretion of local officials.

Regardless of the outcome, there is a significant chance that a large portion of the country will regard whoever sits in the Oval Office come January 2021 as illegitimate.

“Whoever is elected president next week is going to be governing a deeply divided country,” Mr Hudak said.

“If Biden is elected, it’s important to remember that he’s not going to wave a magic wand and right the ship.”