Democrat Joe Biden, his running mate Kamala Harris and Donald Trump's Vice President Mike Pence head to key swing states on Labour Day — kicking off the final stretch of the White House race in a nation battered by the Covid-19 pandemic and facing a historic reckoning on race.

Trump, who rarely stays out of the spotlight for long, was remaining at the White House but announced a surprise news conference for 1:00pm (17:00 GMT), where he was expected to tout some positive financial numbers on a day dedicated to the nation's workers.

"Biggest and Fastest Financial Recovery in History," he said in an early morning tweet.

With less than two months until the November 3 election, the dueling campaigns are anything but traditional, knocked off stride by the multiple layers of turmoil.

Candidates who normally would be skipping daily from state to state to speak before big crowds are limiting their movements and doing much more virtually.

And the sometimes violent anti-racism protests and counter-protests — including one expected later Monday in Portland — lend an explosive and unpredictable element to the campaign.

Biden headed on Monday to Pennsylvania, the state of his birth, where he kicked off with a socially-distant meeting with leaders of the huge AFL-CIO trade union.

At 77, he last week picked up the pace of campaigning but, citing the Covid-19 threat, has been far more cautious than Trump, who at 74 has appeared before hundreds of supporters.

Still, polls show Biden maintaining a persistent, if not insurmountable, lead over Trump, with both men increasingly focusing on key upper Midwest states like Wisconsin, where polling is closer.

Harris, in her highest-profile political sortie since Biden named her running mate, headed to Wisconsin on Monday where she followed in Biden's footsteps by reportedly meeting the family of Jacob Blake — an African American whose shooting by police touched off widespread protests and rioting last month.

The child of immigrant parents, the 55-year-old California senator is both the first black and the first person of Indian descent on a major-party presidential ticket. Black participation dropped in Wisconsin in 2016, and its mobilisation could be key this year.

Harris will also seek to appeal to the important labor vote, meeting with electrical union workers and then black businesspeople in Milwaukee. She is expected to argue that Trump's handling of the pandemic has been incompetent, harming the economy and American workers.

Battling for 

Wisconsin votes 

Pence was also heading to Wisconsin — marking the first time both vice presidential candidates have spoken in the same state on the same day — to deliver remarks to an energy cooperative in the western city of La Crosse.

He is expected to argue that a second Trump term would bring a strong economic revival.

Wisconsin has become a dynamic electoral battleground, even more so after Blake's shooting.

Having seen Hillary Clinton narrowly lose Wisconsin to Trump in a 2016 shocker, Biden and Harris appear determined not to neglect the state's voters.

A racial tinderbox 

Trump, in his news conference, seems likely to be asked about a report in The Atlantic magazine that he has frequently been dismissive of the military and its veterans, charges he angrily denies but which could be damaging, with polling shows his support waning among US troops.

Up to now, the shadow of the coronavirus has produced a somewhat muted campaign, with Biden originally spending so much time in his Delaware home that Trump taunted him about coming out of "his basement".

But the sometimes violent anti-racism protests around the nation, rumbling on unabated and creating a tinderbox situation, are drawing strong words from both presidential candidates.

Trump, blaming the violence on "radicals" and "anarchists", has positioned himself as a law-and-order candidate, openly supporting some right-wing counterprotesters.

Already high tensions in the Oregon city of Portland were further raised Monday by plans for a pro-Trump motorcade into the city, which has seen more than 100 days of protests and two deaths among protesters on either side.

More protests were also expected in the New York city of Rochester, where a black man with psychological problems, Daniel Prude, died after being placed in a hood and forced face-down on a road by police.

Five nights of protests have erupted in the city, whose mayor Lovely Warren has vowed in response to "transform" policing in the city.

Biden recently issued a sharp denunciation of the violence and looting that have accompanied some protests, even while vowing to speak out against racism as the country's "original sin".