Both campaigns reflected that urgency, as Harris and Vice-President Mike Pence each campaigned in Wisconsin, a state Trump narrowly won in 2016.
The events played out against the background of the pandemic, which has upended campaigning and pushed Biden and Harris in particular to conduct much of the traditional election activity online.
While the health of the American economy and status of workers were dominant Labour Day themes, both campaigns also focused on recent protests that have roiled Wisconsin and the rest of the nation.
Harris, the first Black woman on a major party presidential ticket, met privately with Jacob Blake's family at the Milwaukee airport after arriving in the state, where she spoke with Blake by phone from his hospital bed.
Pence touched on the protests during a speech in La Crosse, where he toured an energy facility.
Out on the trail, signs of the pandemic were evident.
While Pence didn't speak with a mask on, workers from the power company he toured did as they stood behind him.
Harris was careful not to stray far from blue "X" marks taped on the floor to encourage social distancing as she toured an International Brotherhood of Electrical Workers training facility.
While supporters gathered outside the candidates' stops, they had minimal interaction with members of the public beyond the people invited to their events.
Harris also met with black business owners in Milwaukee, where she said her day of campaigning was focused on "the dignity of work and the dignity of human beings."
Biden spoke to a small group of labour leaders in a backyard in Lancaster, where he criticised Trump for "refusing to deal with the problems that affect ordinary people" and called for strengthening unions.
His campaign announced endorsements from the Labourers' International Union of North America, the International Union of Elevator Constructors and the National Federation of Federal Employees, collectively representing hundreds of thousands of union workers nationwide.
Later, at an AFL-CIO virtual town hall with union President Richard Trumka, Biden called Trump's alleged remarks about fallen soldiers being "losers" and "suckers" un-American and said Trump would never understand why Americans serve. Trump has denied the remarks.
"He'll never understand you, he'll never understand us, he'll never understand our cops, our firefighters, because he's not made of the same stuff," Biden said.
Earlier in the day, Trump painted Biden as a leader incapable of handling the coronavirus and reviving the economy and pledged his own "undying loyalty to the American worker."
He boasted of adding more than 10 million jobs since May, without mentioning that's only about half of the jobs lost since the pandemic began. He also said the unemployment rate "plunged" to 8.4 per cent.
It was a sharper decline than many economists expected from the prior month, but economists broadly view the latest report as evidence that further economic improvement will be sluggish.
He alleged Biden and Democrats would "immediately collapse the economy."
The day marked Harris' first solo foray onto the campaign trail for in-person events since she became Biden's running mate nearly a month ago.
Biden himself has stepped up his campaigning over the past week, travelling to Pittsburgh and Kenosha and holding two news conferences.
Aides say to expect both Biden and Harris to increase their campaigning for the remaining weeks.
Polls consistently show the economy as an issue at the top of voters' minds.
A strong economy that was Trump's biggest asset for re-election has now become a potential liability, brought down by the coronavirus.
Biden says Trump has had an inadequate response to the pandemic, resulting in more loss of life and jobs than necessary.
The US economy has been steadily rebounding from its epic collapse as many businesses have reopened and rehired some laid-off employees. Yet the recovery is far from complete. Only about half the 22 million jobs that vanished in the pandemic have been recovered.
Economic inequalities also appear to have widened, with lower-income and minority workers suffering disproportionately while affluent Americans have lost fewer jobs and even benefited from rising stock and home prices.
- AP
