President Donald Trump lashed out at "stupid" critics from within his own party and called for unity on Sunday after growing Republican criticism and warnings of a "bloodbath" in the November 3 election.

Trump issued the comments as he and his Democratic opponent Joe Biden hit the ground in crucial swing states in the final stretch before an election that opinion polls show the real estate mogul is at serious risk of losing.

Donald Trump, speaking here at a rally in Janesville, Wisconsin, faces an uphill battle less than three weeks before the election
Donald Trump, speaking here at a rally in Janesville, Wisconsin, faces an uphill battle less than three weeks before the election AFP / MANDEL NGAN

Speaking to a rally in the western state of Nevada, Trump ranged from attacks on Biden and boasts about his economic policies to discussions on bathroom water pressure and a shirt worn by the commissioner of the National Football League.

But he also addressed comments from Republican Senator Ben Sasse of Nebraska, who recently told constituents Trump "kisses dictators' butts," mistreats women and uses the White House as a business.

Other Republicans have warned of electoral losses in the polls that will include congressional races, including Senator Ted Cruz, who like Sasse said there was a risk of a "bloodbath."

Joe Biden boards a plane in Delaware for a campaign day trip to Durham, North Carolina
Joe Biden boards a plane in Delaware for a campaign day trip to Durham, North Carolina AFP / ROBERTO SCHMIDT

Even one of Trump's closest Senate allies, Lindsey Graham, recently said Democrats have a "good chance" at winning the White House.

"We have some stupid people," Trump said at the rally in Carson City, Nevada's capital.

"We have this guy Sasse, you know, wants to make a statement... The Republicans have to stick together better."

An attentive crowd as Donald Trump speaks during a rally in Janesville, Wisconsin
An attentive crowd as Donald Trump speaks during a rally in Janesville, Wisconsin AFP / MANDEL NGAN

Trump, scrambling to make up lost ground, is on a furious multi-state barnstorming tour, hopping on Sunday from Nevada to California and then back to Nevada for a day of rallies and fundraising, before moving on to Arizona on Monday.

Map of the United States showing the percentage of mail ballots returned or in-person early votes by state ahead of the November 3 presidential election
Map of the United States showing the percentage of mail ballots returned or in-person early votes by state ahead of the November 3 presidential election AFP / Jonathan WALTER

An infrequent church-goer, he attended services Sunday in a cavernous -- but not entirely full -- evangelical church in Las Vegas. Congregants prayed for him, and when a collection plate was passed, a pool photographer saw Trump toss in a handful of $20 bills.

Biden, a practicing Catholic, attended Mass with his wife Jill at their church near Wilmington, Delaware, before walking outside to visit the grave of son Beau, who died of brain cancer in 2015.

Limiting his own campaign itinerary due to pandemic concerns, the 77-year-old Biden then flew to North Carolina for a pair of events.

Hundreds of trump supporters in Ocala ahead of a campaign rally in the swing state of Florida.
Hundreds of trump supporters in Ocala ahead of a campaign rally in the swing state of Florida. AFPTV / Gianrigo MARLETTA

In Durham, the mask-wearing former vice president jogged to a stage in a parking lot where people in dozens of vehicles waited for him.

"We choose hope over fear, we choose unity over division, science over fiction and yes, we choose truth over lies," he told them.

His motorcade also made an unannounced stop to allow him and his granddaughter to order milkshakes, with Biden -- keen to play up the stark differences between his campaign and Trump's -- keeping his mask on throughout.

Protesters gather at Dirksen Federal Court Plaza in Chicago ahead of a march to protest the Supreme Court nomination of Judge Amy Coney Barrett and to build momentum to vote President Trump out of the White House
Protesters gather at Dirksen Federal Court Plaza in Chicago ahead of a march to protest the Supreme Court nomination of Judge Amy Coney Barrett and to build momentum to vote President Trump out of the White House AFPTV / Derek R. HENKLE

The candidates' final nationally televised debate will be on Thursday in Nashville, Tennessee.

Their first debate descended into a chaotic stream of interruptions by Trump, head-shaking and angry rejoinders; the second was replaced by dueling town-hall meetings after Trump refused to debate virtually on the heels of his bout with the coronavirus.

The final debate will be face-to-face.

If there was any doubt about the 74-year-old president's own recovery from the virus, his packed campaigning schedule appears to belie it, and his message has -- if anything -- grown more pointed.

On Sunday, Trump again raised a disputed allegation that messages on a laptop computer belonging to Biden's son Hunter implicated the former vice president in corrupt links to Ukraine, calling it a "proven fact."

Biden's campaign has repeatedly rejected the allegations, angrily dismissed by the candidate as a "smear campaign."

But Trump has not backed down.

In a rally Saturday in Muskegon, Michigan, he called Biden "a criminal" and even joined an enthusiastic crowd in chants of "Lock him up!"

Trump also further stoked a US culture war with outlandish claims, saying the Democrats wanted to "erase American history, purge American values and destroy the American way of life."

With the president trailing in polls, some analysts say he should focus on America's economic prospects, which Trump considers his strong point.

Nearly 220,000 Americans have died from Covid-19, the world's worst total, and the outbreak is now spreading in many states at rates unseen in months.

Ahead of Trump's Nevada events, Biden said the president "needs to answer for his failed response to Covid-19."

Trump has dismissed his weak polling data, while Biden's supporters are also wary about over-confidence in an election that could tilt on a close race in a single state such as Florida.

Democrats assailed Trump on Sunday not just for his attacks on Biden but also on Michigan Governor Gretchen Whitmer, the recent target of a kidnapping plot by a heavily armed right-wing militia group.

The president is "incentivizing and inciting this kind of domestic terrorism. It is wrong. It's got to end. It is dangerous," Whitmer told NBC's Meet the Press.