Vice President Kamala Harris will spend all of Monday in Pennsylvania, whose 19 electoral votes offer the largest prize among the states expected to determine the Electoral College outcome.
The Democratic nominee will visit working-class areas including Allentown and end with a late-night Philadelphia rally that includes Lady Gaga and Oprah Winfrey.
Republican nominee Donald Trump plans four rallies in three states, beginning in Raleigh, North Carolina and stopping twice in Pennsylvania with events in Reading and Pittsburgh.
About 78 million people across the US have already made their decision, taking part in early voting. (AP PHOTO)
The former president ends his campaign the way he ended the first two, with a late Monday night event in Grand Rapids, Michigan.
About 78 million people already have voted early but Harris and Trump are pushing to turn out many millions more supporters on Tuesday.
The vice president ascended to the top of the Democratic ticket after President Joe Biden's disastrous performance in a June debate set into motion his withdrawing from the race - just one of a series of convulsions that have hit this year's campaign.
Trump survived by millimetres a would-be assassin's bullet at a rally in Butler, Pennsylvania.
His Secret Service detail foiled a second attempt in September when a gunman had set up a rifle as Trump golfed at one of his courses in Florida.
Harris has pitched herself as a generational change, emphasised her support for abortion rights after the Supreme Court's 2022 decision ending the constitutional right to abortion services and regularly noted the former president's role in the January 6 riots at the US Capitol.
Assembling a coalition ranging from progressives like Representative Alexandria Ocasio-Cortez of New York to Republican former vice president Dick Cheney, Harris has labelled Trump a threat to democracy and late in the campaign even called Trump a "fascist".
Harris posted a video on social media over the weekend in which she showed off having cast her ballot by mail.
"Yes, this race is going to be tight but we are going to win. And one of the reasons why is you're gonna vote," she said.
Trump is planning to cast his ballot in Florida on Tuesday.
The former president, renewing his "Make America Great Again" and "America First" slogans, has made his hard-line approach to immigration and withering criticisms of Harris and Biden the anchors of his argument for a second administration.
He has hammered Democrats for an inflationary economy and has pledged to lead an economic "golden age," end international conflicts and seal the US southern border.
The election is likely to be decided across seven states.
Trump won Pennsylvania, Michigan and Wisconsin in 2016 only to see them flip to Biden in 2020.
North Carolina, Georgia, Arizona and Nevada add the Sun Belt swath of the presidential battleground map.
Trump won North Carolina twice and lost Nevada twice.
He won Arizona and Georgia in 2016 but they were gained by the Democrats in 2020.
Harris' team has projected confidence in recent days, pointing to a large gender gap in early voting data and research showing late-deciding voters have broken her way.
They also believe in the strength of their campaign infrastructure.
This weekend, the Harris campaign had more than 90,000 volunteers helping turn out voters and knocked on more than 3 million doors across the battleground states.
Still, Harris aides have insisted she remains the underdog.
Trump's team has projected confidence as well, arguing that the former president's populist appeal will attract younger and working-class voters across racial and ethnic lines.
The idea is that Trump can amass an atypical coalition, even as other traditional Republican blocs - notably college-educated voters - become more Democratic.
