Over the summer, both men will formally become their parties’ 2024 candidates. But next week the Democratic incumbent and his Republican predecessor will lock horns on CNN.

It will be the first of at least two debates before the 5 November election.

The debate begins at 21:00 EST (01:00 GMT) on Thursday 27 June. It takes place live on CNN from Atlanta, Georgia. The event will also be aired on CNN International, CNN en Español, CNN Max and the CNN website.

Stay tuned for the BBC’s coverage and analysis on our live blog.

The network says it will last 90 minutes and include two commercial breaks. The two candidates flipped a coin on Thursday to determine their podium placement and the order of their closing statements.

The Biden campaign picked tails, and the president has elected to appear at the podium on the right-hand side of the screen, with Trump to his left. But the former president will get the last word at the debate, as he opted for Mr Biden to deliver his closing statement first.

Both candidates will stand for the debate. Reports suggesting that Mr Biden requested a seat for the event are inaccurate, according to his campaign. Campaign staff are not allowed to interact with either candidate over the course of the event, including during each break.

Each man will be given a pen, a pad of paper and a bottle of water – but no props or pre-written notes are allowed on stage. Unlike in their previous showdowns, the candidates will have their microphones muted except for when it is their turn to speak.

There will also be no studio audience – and CNN intends to “enforce timing and ensure a civilised discussion”.

This is the earliest televised US general election debate since 1960. It is also the first one since the late 1980s to not be organised by its traditional host, the bipartisan Commission on Presidential Debates (CPD).

To explain why that is the case, let’s go back four years. Joe Biden and Donald Trump faced off against each other on a stage twice before their 2020 contest. Those two debates were ugly and heated affairs widely panned by viewers.

But for months now, their rematch has looked all but inevitable.

Polling indicates most Americans are not thrilled about that – so the 81-year-old incumbent and his 78-year-old nemesis are keen to build whatever momentum they can with a jaded electorate. They shadow-boxed for several weeks, suggesting neither man wanted to debate the other.

Then, in May, Mr Biden threw down the gauntlet. At the same time, the Biden campaign issued a series of complaints over how the CPD had handled the 2020 debates, criticising it for an antiquated approach for creating “huge spectacles” rather than “good debates”.

It also argued that the CPD-hosted debates take place too late in the cycle, when people in some states have already cast early ballots. Within hours of the challenge, Trump agreed to two debates – the CNN event next week, and a second meeting in September on ABC News.

These events will be based largely on ground rules laid out by the Biden campaign. The Trump campaign has called for more debates, with audiences, but his rival has so far turned down the proposal.

Next Thursday will be the first time either steps on a debate stage in four years.

The window to qualify for this debate closed a minute after midnight on Thursday. CNN says only Mr Biden and Trump satisfied all of its requirements.

To qualify, participants had to:

• Meet the constitutional requirements to serve as president;
• File a formal statement of candidacy with the Federal Election Commission;
• Receive at least 15% in four national polls that meet the network’s standards; and,
• Appear on enough state ballots to meet the threshold of 270 electoral votes needed to win the presidency.

According to CNN, independent presidential candidate Robert F Kennedy Jr did not meet the latter two requirements. The network said he only had three qualifying polls and, because he currently appears on just six state ballots, can only accumulate 89 electoral votes.

Mr Kennedy – who has accused the Biden and Trump campaigns of “colluding” with CNN to exclude him – slammed the decision as “undemocratic, un-American, and cowardly”.

His campaign has loomed large over this race, threatening to pull a sizeable portion of the vote from two unpopular major-party candidates. Other candidates also did not make the cut for CNN’s debate.

Debate prep has begun in earnest for both men – but how they are reportedly going about it looks very different.

Mr Biden is huddling this week and next with some of his closest advisors at Camp David, the rustic presidential retreat in the quiet mountains of Maryland.

In prep sessions, the Democrat is reportedly poring over question-and-answer binders in an effort to frame the election as a choice between two opposites.

Campaign officials have stressed he will continue his new “punchier” approach toward his Republican rival and hold him accountable for his political record.

By contrast, Trump has been participating in a series of “informal policy discussions”, according to his campaign.

In these sessions, he has huddled with lawmakers – including at least two vice-presidential contenders, Marco Rubio and JD Vance – as well as policy experts, senior advisors and outside allies on a range of topics from abortion to crime.

The former president has set the bar very low for his opponent, claiming he is “the WORST debater I have ever faced” and “can’t put two sentences together”.

But he has also suggested the odds will be stacked against him, in part because he says he will be unfairly treated by the media.