WATERFORD, United States — Donald Trump was visiting five swing states on Sunday in a furious blitz of campaigning against challenger Joe Biden with just two days left before a US presidential election that has already drawn a record number of early votes.

Biden focused on Sunday on a state vital to both men: Pennsylvania, where the former vice president plans two socially distanced events in Philadelphia.

The last-minute scramble came as polls showed Biden maintaining his overall lead, but with some tightening in states including Pennsylvania, where he leads by a half-dozen points, and in another key state, Florida, a margin-of-error tossup.

As Trump continued his exhausting whirlwind of appearances, Democrats hammered the president over his handling of the coronavirus pandemic following the country's worst week ever, and with more than 1,000 Americans dying daily.

Yet, the president shrugged off the seriousness of Covid-19 — going so far as to accuse doctors of inflating virus death tolls for profit. More than 230,000 Americans have died in the pandemic.

Trump also continued his extraordinarily open conflict with doctor Anthony Fauci, calling the top government scientist a "disaster."

Fauci spoke out bluntly in an interview to The Washington Post on Sunday saying that without "an abrupt change" in the country's public health practices, Americans face "a whole lot of hurt ahead".

Both parties publicly exuded confidence amid their final dashes to the finish line.

"We're going to know on Election Day that a record number of people have probably turned out to vote in this election because they want change," Biden campaign adviser Anita Dunn said on ABC.

"They want a leader who is going to unite the country, not divide it."

Trump campaign advisor Jason Miller insisted that Trump would sweep Southern states and that if he then takes only one of four key Midwestern states — Pennsylvania, Minnesota, Wisconsin or Michigan — "he will be reelected president".

Trump started an exhausting Sunday schedule with successive rallies in Michigan, Iowa, North Carolina and Georgia before an unusual 11:00pm rally in Florida.

On Monday, both Trump and Biden, as well as their running mates, will converge on Pennsylvania, which Trump won in 2016 by less than one percentage point.

Amid the surge of mail-in ballots to be counted, and with legal challenges likely, Pennsylvania is expected to be a focus of prolonged uncertainty — and anxiety — for days after the election.

Democrats have dominated in early voting, but polls show many Republicans plan to vote in-person on Tuesday.

Republican National Chairwoman Ronna McDaniel insisted on Sunday that the economy — and Trump’s insistence on keeping it open even amid the pandemic — was the central issue.

"Joe Biden is saying we can lock it down, like we’re seeing in Europe, and it will destroy our economy,” she said on CBS. "I think the American people are saying, I can’t afford for the economy to close down.”

Underscoring the high stakes, a record 92 million early votes have already been cast, according to the non-partisan US Elections Project.

Trump, who has repeatedly claimed, without evidence, that mail-in ballots are open to fraud, warned Saturday of "bedlam in our country” if no clear winner emerges quickly in the election.

Biden meanwhile told backers it was "time for Donald Trump to pack his bags and go home”.

The election takes place in a deeply divided country, with feelings so raw that gun sales have surged in some areas. Businesses in some cities, including Washington, are protectively boarding windows, and police are preparing for the possibility of violence.

‘Life or death’ 

The campaign has been overshadowed by the surging pandemic, which even sickened Trump and members of his staff.

In stark contrast to Trump, who has belittled mask-wearing by Biden and others, the Democrat has scrupulously followed the guidance of public health experts.

On Saturday, Biden was joined on the campaign trail in Michigan by his former boss, Barack Obama.

In Trump’s 2016 victory, he took advantage of low turnout rates among Black Michigan voters. As Biden campaigns with the nation’s first Black president, he clearly hopes to change that.

Obama pulled few punches in appearances in the cities of Flint and Detroit, saying 140,000 American lives would have been saved if the president had taken an approach to the pandemic similar to Canada’s.

"This isn’t a sporting event,” the former president said. "This is life or death.”

And Biden said, "We’re done with the chaos, the tweets, the anger, the failure, the refusal to take any responsibility.”

Biden, despite his more cautious and reserved campaign style, has recently pushed Trump onto the back foot in unexpected battlegrounds like Georgia and Texas, a large, traditionally conservative bastion now closer to being a toss-up.