Joe Biden and Donald Trump square off in a US presidential debate that carries enormous stakes for both candidates as they battle for any advantage in their tight race for the White House.
Millions of Americans tune in for a clash taking place months earlier than usual -- the opening salvo in what promises to be a bruising summer of campaigning, in a deeply polarized country still scarred by the chaos and violence of the 2020 election.
With only two debates this election cycle and national polls showing the pair locked in the tightest of contests, the event at CNN headquarters in Atlanta takes on heightened significance.
For many voters, the choice between the 81-year-old Biden, the oldest ever incumbent, and the 78-year-old Trump, now a convicted felon, is an uninspiring one -- a dynamic both candidates need to counter.
For Trump, an instinctive political pugilist, the challenge will be to rein in the aggressive tendencies he unleashed -- to his detriment -- in their first chaotic debate four years ago.
The Democratic president will be desperate to avoid any major gaffes that could underline concerns about his age.
He also will focus on his key campaign message that Trump poses an existential threat to US democracy.
There is certainly no love lost between the two candidates, and both sides have agreed to debate rules aimed at minimizing the prospect of a shouting match.
There will be no studio audience, depriving them of the momentum that comes from ginning up supporters, and microphones will cut out when a candidate's speaking time is over.
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