Donald Trump was on his golf course wearing a Make America Great Again cap when the verdict on the 2020 US election finally came. After four days of tense vote counting – and four tumultuous years in the White House – the end of the Trump presidency arrived about 11am local time (3am AEDT).

Democrat Joe Biden had smashed through Trump’s early leads in key battleground states to claim the 270 Electoral College votes needed, becoming the first candidate to defeat a one-term president in a quarter of a century.

But, as the nation erupts in celebration and world leaders congratulate Biden, Trump is now doing exactly what he had threatened to do long before election day – he’s not conceding. He’s going to court. And he’s tweeting up a storm, insisting he won the election and doubling down on his unfounded claims of voter fraud.

Commentators, including former Australian prime minister Malcolm Turnbull, think it unlikely Trump will barricade himself in the Oval Office if his demands for recounts and vote disqualifications fail (as expected) to change the result.

But concerns remain about whether there can be the usual peaceful transition of power by inauguration day on January 20.

So why does Trump think a vote for Biden is “illegal”, will recounts make a difference and could he (or a judge) really overturn the result?

Why is Trump claiming electoral fraud?

First, his election night demand to call off vote counting sent a shiver through Western democracies. Now he wants to have certain votes ruled invalid. He had foreshadowed and filed lawsuits to this end well before Americans went to the polls. Here’s the Trump strategy:

This year’s election saw record voter turnout for both candidates (Biden, for example, won more than 74 million overall votes, the most of any candidate in history). Yet, in a country ravaged by the pandemic, a record number of those votes also came via the mail.

Postal voting has been built into the state's well-honed electoral systems for decades without concern, says Dr Thomas J. Adams, an expert in US politics and history at the University of Sydney. But in many states, these mail-in ballots are counted after those from polling booths, and the sheer volume this year has slowed counting overall, even as officials worked around the clock.

That meant the overall election result took longer to crystallise because historically these mail-in ballots also skew Democrat – hence the terms the “red mirage” and “blue wave”, where early election results can show the map filling up with red Republican votes, only to be washed away by blue Democrat mail-in ballots counted later. Trump insists this well-known phenomenon is instead evidence of voting fraud and he’ll be taking it all the way to the highest court in the land: the Supreme Court.

Adams, like many experts, sees Trump's threat as a ploy from a President and businessman with a long history of pursuing lawsuits - the longer vote counting continued, and the more unrest built in the streets of a nervous America, the more chance Trump's army of lawyers had of getting certain mail-in ballots disqualified. But with final tallies skewing more and more for Biden and legal bids to halt the count in states such as Michigan and Pennsylvania quickly rejected by courts, even a successful bid to throw out a few-thousand votes in the next few weeks won't move the dial back to Trump.

"But it's about casting doubt on the result too," Adams says. "It's part of how [Trump] operates. He throws things out there and sees what sticks. It doesn't mean he can do it."

Vote counting commonly continues after election night - American democracy is a big logistical undertaking requiring enormous manpower. That’s why states have their own inbuilt deadlines to finish counts and until December 14 to certify their vote to Congress. Final tallies in knife-edge races such as Georgia and Arizona are still being completed even now Biden has won, and a small number (about 1700) of missing ballots have already turned up in states such as Pennslyvania after a state court ordered the US postal service to conduct sweeps - of course this was because the Postmaster General, a Trump appointee and former Republican fundraiser, declined to conduct those checks to begin with.

But in the wee hours of the morning after election night, when millions of votes were still to be counted (legally), Trump prematurely declared victory. If he didn't win, he told Americans, it was because they had been the victim of a "massive fraud" and he has since unleashed an extraordinary tirade of unfounded allegations against electoral officials – even in states with Republicans running the show, such as Georgia. Some Trump supporters have already responded, surrounding voting centres and taking to the streets with at times conflicting messages – either to demand vote counting stop or for media networks to hold off declaring a winner until it's completely done.

No system is perfect. Voting fraud and mistakes do happen in US elections, but it's rare. Adams notes tactics to stop certain people voting in the first place, such as those straight out of Republican playbooks to increase barriers for minorities, have a much bigger impact on final tallies.

Officials, and even some Republicans, say they have seen no evidence of fraud or tampering in this election, which has been one of the most closely scruntised in history. The only cases disclosed so far by authorities involve two Republican voters attempting to vote twice, in Nevada and Pennsylvania. Officials have hit back at lawsuits filed in Nevada claiming votes were cast for dead people and those out of area. And in Georgia, a judge has already thrown out a case alleging 53 late-arriving ballots (which must be thrown out under Georgia law) were seen to be mixed in with those for counting. (The Republican witnesses in question later admitted they had no evidence either.) Despite Trump’s accusations of corruption in Georgia's electoral apparatus, the top election chief there is a Republican and has stressed they are following all the state rules, though a recount is still likely as the tight margin between candidates is expected to stay within the 0.5 per cent threshold needed to trigger one.

Will recounts change the result?

So a recount looks to be on the cards for Georgia and Trump's team have already announced they will file for one in the midwestern state of Wisconsin, where the margin between the candidates is within that state's recount threshold of 1 per cent or less. (That still adds up to more than 20,000 votes between them.) A challenge in Nevada, where the race was also tight and recount laws are fairly relaxed, is likely too (Biden claimed the state with a 27,000 lead). While Arizona remains close, its top election official thinks it unlikely the margin will shrink far enough to meet the state's own stricter threshold for a redo. (Biden was up by about 15,000 votes as of November 11. Arizona recount maths dictates a recount will only be triggered if the difference between the candidates is equal to or less than one-tenth of 1 per cent of the total number of votes cast.)Biden's winning lead in Pennsylvania too seems to have passed the threshold for an automatic recount (a 0.5 per cent or less margin).

Recounts are not uncommon in the wild world of US politics, but rarely do they change more than a few-hundred votes. Adams says right now the margins at play are nowhere near as close as they were during the now infamous 2000 election between Democrat Al Gore and Republican George W. Bush – back then the entire Electoral College tally came down to just one state (Florida) and a margin of 537 votes, the closest in US history.

Trump would have to win a suite of these recounts to change the outcome of the election – a scenario experts deem virtually impossible. But if Trump does pull it off, winning key recounts, Adams says he may have another trick up his sleeve for the state that decided the presidency when it turned blue for Biden this weekend: Pennsylvania.

Can the Supreme Court overrule Biden's win?

While there is precedent for the Supreme Court to intervene, such as when it ruled in favour of Bush in the 2000 race, Trump cannot just walk into the courthouse right now and file a petition to throw out votes. Challenges have to work their way up through a gauntlet of state courts first, including district, and there have to be clear legal grounds for a case.

The key opening for Trump’s lawyers lies in the expanded postal voting rules in many states this year under COVID-19. Before the election, Republicans had already been busy fighting a suite of lawsuits across the country to invalidate certain postal votes. Pennsylvania is among states that decided to count ballots received up to three days after election day so long as they were clearly postmarked for November 3. A Republican challenge to this rule made it all the way to the Supreme Court in October. The bench was deadlocked and declined to fast-track it then (Trump's recent conservative pick Amy Coney Barrett, the ninth justice, had yet to arrive), but the court indicated it could reconsider the matter and so the votes in question were clearly marked. But the state's top election official has said they do not appear to be in high enough numbers to affect the outcome of the state's result.

In terms of a bigger, more national challenge, some in Trump's camp push the line that all of these new COVID rules on voting have not been legislated specifically under state laws, and therefore all relevant ballots should be ruled invalid. Adams notes the new pandemic rules were made – and then challenged by Republicans – well before election day. "They've tried and failed there already. We've passed the moment for a proper reckoning." But if a number of cases did make it before "the Supremes", out of states deciding the election, and the court decided they were the same issue, then the new conservative lean to the bench could work in Trump's favour.

"But it doesn't mean they'll automatically [help him]," Adams says. "I haven't seen any [legal argument] that looks like it would stand up...and it's got to be enough votes to actually change the result."

Already, the Trump campaign's supposed "whistleblower" poll worker who alleged improper vote counting in Pennslyvania has admitted his sworn testimony was made up. Now the campaign has filed another lawsuit in the state - this time to block officials from certifying the final vote count entirely. It's raised the spectre of an even wilder final move Trump could try - to formally elect a president, each state's "electors" (both Republican and Democrat) cast their votes in Congress on December 14.

Professor of Law in Texas Lynne Rambo says changing that vote from Biden to Trump would mean convincing a lot of people (including Democrats) in key states to overturn the will of their electorates - another almost impossible task. In Georgia, the Republican election chief has already indicated he will be voting in line with his state's final tally.

Rambo offers this observation of the dying days of the Trump presidency: "This entire administration, the courts have been the only thing keeping Trump at least somewhat under control...The only place where the lies and the wild accusations without evidence don’t fly. My concern is that he may actually use a loss in the courts as his final act in declaring, without any basis, every American institution corrupt. "

Any chance of that concession speech?

Even with legal doors closing in Trump's face and the nation's election analysts (or "chart-throbs") all calling the race for Biden, the President's associates have said privately that he is unlikely to formally concede the race in the traditional manner (though CNN reports senior adviser Jared Kushner has approached the President about doing so). Some worry Trump may even try to scuttle plans for a Biden handover. The President is in debt and already facing lawsuits when he leaves office (in the fine print of recent emails from Team Trump appealing for last-minute legal fee fundraising is a note about paying off the campaign's debts as well).

Over the weekend, Trump rejected Biden's win, saying the election was "not over" and that legal challenges would continue on Monday. When networks began to call the race for Biden, Trump's lawyer Rudy Giuliani was doubling down on voting fraud allegations at a press conference at the Four Seasons in Philadelphia- which, in a surprise twist, turned out not to be the luxury hotel but the carpark of Four Seasons Total Landscaping, a landscaping business next door to an erotic store.

As for the logistics of a presidential transition, experts say the law doesn’t need a formal concession for the handover to start – a more obscure branch of government, the General Services Administration, will give the OK, which it has not yet done (the Washington Post reports it may be under pressure from the White House to now delay.) Still Trump refusing to give the speech or make the usual call to his opponent is more akin to a sportsperson refusing to shake hands with the winning team after a game than a serious block in the democratic machine. If Trump doesn't go quietly come January 20, Biden has said he trusts the secret service will show him the door.

White House spokesman Judd Deere emphasised that transition co-ordination with Biden's team has been under way for months as required by federal law – Biden has already been granted 900 square metres of office space at the Commerce Department and the Trump administration is "following all statutory requirements". Trump "will accept the results of a free and fair election", he said.

Of course, what is free and fair to Donald Trump may not match the rest of the country’s reality. One man's Four Seasons, is another man's Total Landscaping...