Opinion polls show the pair locked in a tight race, with Vice President Harris, 60, bolstered by strong support among women voters while former President Trump, 78, gains ground with Hispanic voters, especially men.
Voters overall view both candidates unfavourably, according to Reuters/Ipsos polling, but that so far has not dissuaded them from casting ballots.
More than 77 million Americans have already done so ahead of Election Day on Tuesday, according to the University of Florida's Election Lab, approaching half the total 160 million votes cast in 2020, in which US voter turnout was the highest in more than a century.
Control of the US Congress is also up for grabs on Tuesday, with Republicans favoured to capture a majority in the Senate while Democrats are seen as having an even chance of flipping Republicans' narrow majority in the House of Representatives. Presidents whose parties have not controlled both chambers have struggled to pass major legislation over the past decade.
"In just two days we have the power to decide the fate of our nation for generations to come," Harris told parishioners at Greater Emmanuel Institutional Church of God in Christ in Detroit on Sunday.
"We must act. It's not enough to only pray; not enough to just talk. We must act on the plans He has in store for us, and we must make them real through our works, in our daily choices, in services to our communities, in our democracy."
Later in a rally in East Lansing, Michigan, she addressed the state's 200,000 Arab Americans, starting her speech with a nod to civilian victims of Israel's conflict with Hamas in Gaza and Hezbollah in Lebanon.
"This year has been difficult, given the scale of death and destruction in Gaza and given the civilian casualties and displacement in Lebanon, it is devastating. And as president, I will do everything in my power to end the war in Gaza," Harris said to applause.
Later in a rally in East Lansing, Michigan, she addressed the state's 200,000 Arab Americans, starting her speech with a nod to civilian victims of Israel's conflict with Hamas in Gaza and Hezbollah in Lebanon.
"This year has been difficult, given the scale of death and destruction in Gaza and given the civilian casualties and displacement in Lebanon, it is devastating. And as president, I will do everything in my power to end the war in Gaza," Harris said to applause.
She faces scepticism from some who are frustrated that Harris has not done more to help end the war in Gaza and scale back aid to Israel. Trump visited Dearborn, Michigan, the heart of the Arab American community, on Friday and vowed to end the conflict in the Middle East without saying how.
Samah Noureddine, 44, a Lebanese American from Grosse Ile, a town near Detroit, said she voted for Biden in 2020 but was casting a ballot for Jill Stein of the Green Party this year.
"I'm upset because Harris is funding the genocide and if we get Trump we're going to suffer too," she said. "I'm sick of both of them."
Trump goes off script
Trump, at his first of three rallies on Sunday, frequently abandoned his teleprompter with off-the-cuff remarks in which he denounced polls showing movement for Harris. He called Democrats a "demonic party," ridiculed Democratic President Joe Biden and complained about the price of apples.
Trump, who survived an assassination attempt in July when a gunman's bullet grazed his ear in Butler, Pennsylvania, on Sunday complained to supporters about gaps in the bulletproof glass surrounding him as he spoke and mused that an assassin would have to shoot through the news media to get him.
"To get me, somebody would have to shoot through the fake news and I don't mind that so much," said Trump, who has long criticised the media and sought to rile public sentiment against them.
Last week he suggested prominent Republican critic former congresswoman Liz Cheney should face gunfire in combat over her hawkish foreign policy, leading an Arizona prosecutor to open an investigation.
Campaign spokesperson Steven Cheung issued a statement saying Trump was not directed toward the media but rather, "It was about threats against him that were spurred on by dangerous rhetoric from Democrats."
Trump later spoke in Kinston, North Carolina, and was ending his day with an evening rally in Macon, Georgia.
Of the seven US states seen as competitive, Georgia and North Carolina are the second-biggest prizes up for grabs on Tuesday, with each holding 16 of the 270 votes a candidate needs to win in the state-by-state Electoral College to secure the presidency. Pennsylvania is first with 19 electors.
Nonpartisan US election analysts reckon Harris would need to win about 45 electoral votes in the seven swing states to win the White House, while Trump would need about 51, when accounting for the states they are forecast to win easily.
Near the end of his Pennsylvania speech, Trump - whose false claims that his 2020 loss was the result of fraud inspired his supporters' assault on the US Capitol on January 6 in 2021 - mused that he would have preferred not to have handed over power.
"We had the safest border in the history of our country the day that I left. I shouldn't have left. I mean, honestly, because we did so, we did so well," Trump said.
Trump said during his remarks that election results should be announced on Election Night, despite warnings by officials in multiple states that it could take days to ascertain the final outcome.
Democrats say they have plans in place should Trump try to prematurely claim victory this time.
