Kamala Harris and Donald Trump will meet for the first time face-to-face for perhaps their only debate in the US presidential election, a high-pressure opportunity to showcase their starkly different visions for the country after a tumultuous campaign summer.

The event, at 9pm local time on Tuesday in Philadelphia, will offer Americans their most detailed look at a campaign that has dramatically changed since the last debate in June.

In rapid fashion, President Joe Biden bowed out of the race after his disastrous performance, Mr Trump survived an assassination attempt and both sides chose their running mates.

Signage at the media filing centre ahead of the presidential debate between Republican presidential candidate Donald Trump and Democratic presidential nominee Kamala Harris in Philadelphia
Signage at the media filing centre ahead of the presidential debate between Republican Donald Trump and Democrat Kamala Harris in Philadelphia (Pablo Martinez Monsivais/AP)

Ms Harris is intent on demonstrating that she can press the Democratic case against Mr Trump better than Mr Biden did.

Mr Trump, in turn, is trying to paint the vice president as an out-of-touch liberal while trying to win over voters sceptical he should return to the White House.

The 78-year-old has struggled to adapt to Ms Harris, 59, who is the first woman, black person and person of South Asian descent to serve as vice president.

The Republican former president has at times resorted to invoking racial and gender stereotypes, frustrating allies who want Mr Trump to focus instead on policy differences with Ms Harris.

The vice president, for her part, will try to claim a share of credit for the Biden administration’s accomplishments while also addressing its low moments and explaining her shifts away from more liberal positions she took in the past.

The debate will subject Ms Harris, who has sat for only a single formal interview in the past six weeks, to a rare moment of sustained questioning.

“If she performs great, it’s going to be a nice surprise for the Democrats and they’ll rejoice,” said Ari Fleischer, a Republican communications strategist and former press secretary to President George W Bush.

“If she flops, like Joe Biden did, it could break this race wide open. So there’s more riding on it.”

Signage is installed at the media filing centre ahead of the presidential debate between Republican presidential candidate Donald Trump and Democratic presidential nominee Kamala Harris in Philadelphia
Signage is installed at the media filing centre ahead of the presidential debate between Donald Trump and Kamala Harris (Pablo Martinez Monsivais/AP)

Tim Hogan, who led Senator Amy Klobuchar’s debate preparations in the 2020 Democratic presidential primaries, said Ms Harris, a former California attorney general, would bring a “prosecutor’s instincts to the debate stage”.

“That is a very strong quality in that setting: having someone who knows how to land a punch and how to translate it,” Mr Hogan said.

The first early ballots of the presidential race will go out just hours after the debate, hosted by ABC News.

Absentee ballots are set to be sent out beginning on Wednesday in Alabama.