Joe Biden and Donald Trump are preparing to share a stage for the first time in four years.
The president and his predecessor will face off in an extraordinarily early election debate, more than four months before Americans vote on November 5.
If their history is any guide, it's likely to be tense and hostile, and — despite measures designed to keep things on track — could get chaotic.
This is how it will work
The debate is scheduled to kick off at 11am Friday, AEST — that's 9pm Thursday on America's east coast, and 6pm on the west coast.
It's the first of two debates Biden and Trump have agreed to. (The second is set for September.)
It'll be held in Atlanta, Georgia, at the headquarters of broadcaster CNN. Two of the network's big stars, Jake Tapper and Dana Bash, will moderate the debate. But there won't be a studio audience.
It'll go for 90 minutes, with two ad breaks, CNN says.
The Biden and Trump camps have agreed on some rules
The candidates' podium positions have been decided by a toss of a coin: Trump will stand on the left of screen, Biden on the right.
Their microphones will be muted when it's not their turn to speak (to prevent the chaos that characterised the first debate in 2020).
Campaign staff cannot interact with their candidates, even during the ad breaks.
The candidates are not allowed to bring notes (but they can write some down — they'll be provided with a pen and paper).
Props are banned.
Bash and Tapper will ask the questions, but CNN says the debate "is not the ideal arena for live fact-checking" and the hosts will simply facilitate, rather than participate.
This hasn't always gone well
Biden and Trump debated twice during the 2020 campaign. Nobody was too happy with how the first debate went.
Loading...Biden was frustrated by how much he was interrupted by Trump. "It's hard to get a word in with this clown," Biden complained at one point.
Trump was angered when he was called out for his constant interjections by the moderator, Chris Wallace from Fox News. (Wallace has since moved to CNN.)
"I'm just sad with the way last night turned out," Wallace told the New York Times the next day. "I never dreamt that it would go off the tracks the way it did."
Organisers brought in microphone-mute buttons for the next debate — but it was cancelled, because Trump had COVID.
The final debate in 2020 was more orderly than the first. There were still some personal attacks, but the candidates also discussed the campaign's big issues, including the pandemic, foreign adversaries, race relations and climate change.
Loading...Longstanding tradition has been dumped
Since 1988, America's presidential debates have been organised by the bipartisan Commission on Presidential Debates (CPD).
But not this time.
The CPD released a 2024 debate schedule last year, but the Biden campaign said he wouldn't be taking part.
They said the commission was "out of step", its audiences made for "noisy spectacles", and the debates needed to be earlier in the campaign. (Past debates have always been held in September and October, so this one will be the earliest ever.)
The opposing campaigns instead negotiated directly with each other, and with CNN and America's ABC, and sidelined the commission for the first time in 35 years.
CNN will allow other media organisations to broadcast its debate live, so multiple American channels and foreign networks will air it.
There have been some intense preparations
Biden has spent much of the past week at his Camp David retreat. According to the New York Times, an aeroplane hangar and movie theatre have been "outfitted with lights and production equipment to create a mock debate stage".
At least 16 current and former aides have been involved in strategy sessions at the retreat. Lawyer Bob Bauer has role-played Trump in mock debates against Biden, as he did in 2020.
Trump was asked about his preparation strategy just before a campaign rally in Philadelphia at the weekend. "This is really the best strategy right here," he said. "We have all these people screaming questions."
On stage, he asked the Philadelphia crowd: "How should I handle him? Should I be tough and nasty and just say, 'You're the worst president in history'? Or should I be nice and calm and let him speak?"
He's been throwing some early blows, not only at Biden but also at CNN, a network he's long derided as "fake news".
He's already accusing Bash and Tapper of anti-Trump bias and framing the debate as "three against one".
And a CNN host terminated an interview with one of his campaign spokespeople when she started making similar criticisms.
There's a lot to talk about
Biden and Trump deeply dislike one another personally, and differ on almost every major policy position.
America's role on the world stage — including its involvement in Ukraine and Gaza — will feature heavily in the campaign to be commander-in-chief. Abortion and immigration are again shaping up to be major domestic issues. And many Americans will be looking for solutions to cost-of-living issues and concerning crime rates.
But a lot of the focus is likely to be on the men themselves. Trump frequently rails against Biden as the worst president in American history, and regularly questions the 81-year-old's mental fitness to hold office. (Trump turned 78 earlier this month.)
Biden says Trump, with his retribution plans and attacks on the legal and electoral systems, represents a threat to democracy. Trump is also awaiting sentencing for falsifying business records to disguise a hush money payment, and has three other criminal trials pending.
The debate will be broadcast on the ABC News Channel, and ABC News will be live blogging the debate, including the lead-up and the aftermath, from Friday morning.