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

The event, at 9 pm Eastern in Philadelphia, will offer Americans their most detailed look at a campaign that's dramatically changed since the last debate in June. In rapid fashion, President Joe Biden bowed out of the race after his disastrous performance, Trump survived an assassination attempt and bothsides chose their running mates.

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

Trump, 78, has struggled to adapt to 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 Trump to focus instead on policy differences with 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 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.”

Tim Hogan, who led Sen. Amy Klobuchar's debate preparations in the 2020 Democratic presidential primaries, said 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," 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 Wednesday in Alabama.

Trump plans to hit Harris as too liberal

Trump and his campaign have spotlighted far-left positions she took during her failed 2020 presidential bid. He's been assisted in his informal debate prep sessions by Tulsi Gabbard, the former Democratic congresswoman and presidential candidate who tore into Harris during their primary debates.

Harris has sought to defend her shifts away from liberal causes to more moderate stances on fracking, expanding Medicare for all and mandatory gun buyback programmes — and even backing away from her position that plastic straws should be banned — as pragmatism, insisting that her “values remain the same.” Her campaign on Monday published a page on its website listing her positions on key issues.

The former president has argued a Harris presidency is a threat to the safety of the country, highlighting that Biden tapped her to address the influx of migrants as the Republican once again makes dark warnings about immigration and those in the country illegally central to his campaign. He has sought to portray a Harris presidency as the continuation of Biden's still-unpopular administration, particularly his economic record, as voters still feel the bite of inflation even as it has cooled in recent months.

Trump's team insist his tone won't be any different facing a female opponent.

“President Trump is going to be himself,” senior adviser Jason Miller told reporters during a phone call Monday.

Gabbard, who was also on the call, added that Trump “respects women and doesn't feel the need to be patronising or to speak to women in any other way than he would speak to a man.”

His advisers suggest Harris has a tendency to express herself in a “word salad” of meaningless phrases, prompting Trump to say last week that his debate strategy was to “let her talk.”

The former president frequently plows into rambling remarks that detour from his policy points. He regularly makes false claims about the last election, attacks a lengthy list of enemies and opponents working against him, offers praise for foreign strongmen and comments about race, like his false claim in July that Harris recently “happened to turn Black.”

Harris wants to argue Trump is unstable and unfit

The vice president, who has been the Biden administration's most outspoken supporter of abortion access after the Supreme Court overturned Roe v. Wade in 2022, is expected to focus on calling out Trump's inconsistencies around women's reproductive care, including his announcement that he will vote to protect Florida's six-week abortion ban in a statewide referendum this fall.

Harris was also set to try to portray herself as a steadier hand to lead the nation and safeguard its alliances, as war rages in Ukraine more than two years after Russia's invasion and Israel's war with Hamas in Gaza drags on with no end in sight.

She is likely to warn that Trump presents a threat to democracy, from his attempts in 2020 to overturn his loss in the presidential election, spurring his angry supporters to attack the US Capitol on January 6, 2021, through comments he made as recently as last weekend. Trump on social media issued yet another message of retribution, threatening that if he wins he will jail “those involved in unscrupulous behaviour,” including lawyers, political operatives, donors, voters and election officials.

Harris has spent the better part of the last five days ensconced in debate preparations in Pennsylvania, where she participated in hours-long mock sessions with a Trump stand-in. Ahead of the debate, she told radio host Rickey Smiley that she was workshopping how to respond if Trump lies.

“There's no floor for him in terms of how low he will go,” she said.