Trump, aiming to avoid becoming the first incumbent president to lose a re-election bid since fellow Republican George H.W. Bush in 1992, kept up a frantic pace with rallies in Michigan, Iowa and North Carolina, and had later stops planned in Georgia and Florida.
Biden leads in national opinion polls, although the race is seen as close in enough battleground states that Trump could achieve the 270 votes needed to win in the state-by-state Electoral College that determines the victor.
The former vice president made two appearances in closely contested Pennsylvania, the state where he was born and that is crucial to his quest for the White House.
"We're at an inflection point. So we have to vote like we never did before," Biden told a drive-in rally in a parking lot outside a Philadelphia church, where supporters honked their car horns in approval.
Buffeted by snow flurries in Washington, Michigan, a town north of Detroit, Trump wore his trademark red cap emblazoned with the words "Make America Great Again" and was bundled up in an overcoat as he addressed a boisterous crowd on a blustery morning.
After the crowd loudly chanted: "We love you," Trump responded: "I love you, too. If I didn't, I wouldn't be standing here because it's freezing out here."
"You better get out there and vote," Trump told the crowd.
Trump predicted he would repeat his 2016 victory in Michigan and touted his efforts to create auto jobs, a key issue for the auto manufacturing state.
"We brought back your car industry. Your car industry was finished. You would have had nothing left," Trump said.
Motor vehicle manufacturing employment in Michigan has fallen by about 5,000 jobs since Trump took office in early 2017, and there are about 13,000 fewer jobs making vehicle parts.
Trump addressed another spirited rally in windy Dubuque, where he made his pitch to Iowa farmers in the important corn-growing state and predicted he would win there as he did four years ago.
TUSSLES IN TEXAS
Between campaign stops in Philadelphia, Biden criticized Trump for encouraging his supporters after they harassed a Biden campaign bus in Texas. A caravan of vehicles bearing Trump campaign flags surrounded the bus carrying campaign staff on a highway on Friday, forcing the campaign to cancel two events.
Trump on Saturday retweeted a video of the incident and wrote: "I LOVE TEXAS!"
"We've never had anything like this. At least we've never had a president who thinks it's a good thing," Biden told reporters.
The FBI said on Sunday it had opened an inquiry into the Texas incident.
Commenting on an Axios report that Trump has told confidants he will declare victory on Tuesday night if it looks like he is ahead even if the Electoral College outcome is unclear, Biden said: "The president’s not going to steal this election."
Trump told reporters the report was false but said it was a "terrible thing" that ballots would be counted after Tuesday's election.
Biden is ahead 51% to 43% nationally in the latest Reuters/Ipsos poll, taken from Oct 27 to 29. A coronavirus pandemic that has killed more than 230,000 Americans and battered the economy has weighed on Trump's campaign.
But the race remains a toss-up in Florida, North Carolina and Arizona, Reuters/Ipsos polls showed, as Trump trails by 7 percentage points in Pennsylvania and 10 points in Michigan and Wisconsin.
In his 2016 victory over Democrat Hillary Clinton, the real estate developer and reality TV personality-turned-politician was propelled into the White House by victories in Pennsylvania, Wisconsin and Michigan, states that for decades had gone into the Democratic column.
Biden is scheduled to appear again on Monday in Pennsylvania and added a stop in Ohio, indicating his campaign views that Midwestern state as winnable.
A record-setting 93.2 million early votes have been cast either in-person or by mail, according to the U.S. Elections Project, representing about 40% of eligible voters. The early surge has led Michael McDonald of the University of Florida, who administers the project, to predict a record turnout rate of about 65% of eligible voters, the highest rate since 1908.
Trump was due to stage 10 rallies - five a day - on Sunday and Monday, the campaign's busiest stretch, with Monday appearances planned in North Carolina, Pennsylvania, Wisconsin and back in Michigan.
Hitting on familiar themes, Trump portrayed himself as running against "a corrupt politician" and "a dummy and a half" in Biden as well as a "left-wing mob" and Democratic "maniacs."
The contest has proven unexpectedly close in Texas, typically a reliable Republican state.
In Democratic-leaning Houston, a Republican state legislator and a conservative activist are seeking a court ruling that drive-through voting is illegal and that about 120,000 votes already cast should be thrown out. The Texas Supreme Court declined on Sunday to hear their claims. A federal judge is due to hold an emergency hearing on Monday on their request.
