Kamala Harris and Donald Trump made their final preparations Monday on the eve of their first -- and possibly only -- televised debate before the knife-edge 2024 US presidential election.
With less than two months until election day, the face-off could be a turning point in a bitter contest between the Democratic vice president and Republican former president.
Harris arrives at 4.40pm (2040 GMT) Monday in the eastern city of Philadelphia where the debate takes place, while Trump is not due to touch down until hours before Tuesday evening's clash on ABC News.
The two candidates have never even met before, and the debate is set to be a contrast in styles between a former prosecutor and a convicted felon who has targeted Harris with racist and sexist insults.
"There's no floor for him in terms of how low he will go and we should be prepared for that," Harris told radio host Rickey Smiley in an interview broadcast Monday, when asked how she planned to handle Trump's attacks.
"And we should be prepared for the fact that he is probably going to speak a lot of untruths."
Yet Harris in some ways has the most to prove, despite the scandals dogging a rival who has hinted that he won't accept the result of November's election if he loses.
The 59-year-old Harris's honeymoon after replacing the aging Joe Biden at the top of the ticket appears to be fading, with polls showing she needs to reach out to voters who don't know much about her policies.
She addressed the growing pressure late Sunday when her campaign put out a policy page, touching on subjects from unions and cost-of-living issues to health care.
Trump, 78, will be under pressure to rein in his insults and aggression as he goes up against a mixed-race candidate vying to be the first female president in US history.
But he has experience on his side, with six prior presidential debates under his belt -- and his restrained approach against an imploding Biden in their debate in June proved brutally effective.
Biden was forced to drop out of the White House race less than a month later.
Trump struck a typically dark tone in rallies and social media posts over the weekend as he reached out to his right-wing base, at one point warning of "long prison sentences" on all those he said were planning "cheating" in November.
The Harris campaign targeted Trump in an ad on Monday featuring former vice president Mike Pence and other ex-cabinet members saying he was "not fit to be president again "
Pence fell out with Trump after refusing to endorse the then-president's bid to overturn his 2020 election loss to Joe Biden.
Her team said it was also "blanketing" Philadelphia ahead of the debate with billboards and flyers to highlight the "dangers" of Trump's "extreme" policies.
The contrast in styles between Trump and Harris is also reflected in their debate prep.
Harris has been holed up for most of the last five days in a hotel in Pittsburgh -- like Philadelphia in the crucial swing state of Pennsylvania -- doing intense debate practise sessions with her staff.
Trump, who survived an assassination attempt in July, has reportedly taken a more relaxed approach involving a handful of sessions and more informal time with staff during which staff refresh him on his record.
Both will know the high stakes of what is so far the only scheduled debate in the shortest election campaign in modern US political history.
The most recent polls show the race remains on a knife-edge. A New York Times/Siena poll on Sunday found that Trump is leading Harris nationally by 48 to 47 percent, well within the margin of error.
An ABC News poll/Ipsos poll on Monday showed Harris leading Trump 50 to 46 percent.
