President Donald Trump on Monday barnstormed Pennsylvania with three mass rallies Monday and his Democratic opponent also made a surprise appearance, hoping to defend his lead in a swing state that could well decide the outcome of the election in eight days.

Hopping from rally to rally, Trump demonstrated how badly he wants to claim the state on November 3, telling large, enthusiastic crowds of supporters to ignore polls showing Biden leading there and across other battleground states.

US President Donald Trump is campaigning heavily in Pennsylvania, a must-win state
US President Donald Trump is campaigning heavily in Pennsylvania, a must-win state AFP / SAUL LOEB

"We get Pennsylvania, we win the whole thing," he said in Allentown, before flying to another rally in Lititz, then a final event in Martinsburg in the evening.

Trump touted a poll from Rasmussen, which has long gone against the flow of more established polling companies to give him favorable numbers, and said many "hidden Trump voters" would back him in the polling booth on November 3.

Biden, who has maintained a startlingly low profile during his campaign, made a surprise appearance in the Pennsylvania town of Chester, making the short trip from his home in neighboring Delaware where he'd been scheduled to spend the day without public events.

President Donald Trump said opponent Joe Biden will 'abolish' the US oil industry
President Donald Trump said opponent Joe Biden will 'abolish' the US oil industry AFP / SAUL LOEB

Sticking to his main campaign theme, he hammered Trump's response to the Covid-19 pandemic, accusing him of giving up on mastering the virus.

"He said we're not going to control it. The bottom line is Donald Trump is the worst possible president, the worst possible person to try to lead us through this pandemic," Biden said. Trump "doesn't have any idea of what to do or he just doesn't care."

"Mr president, you have to have a little bit of shame, just a little bit of shame, because people are dying," Biden said.

Democratic presidential nominee Joe Biden is lower key but believes that anger over the coronavirus will sweep him to victory
Democratic presidential nominee Joe Biden is lower key but believes that anger over the coronavirus will sweep him to victory AFP / Angela Weiss
Voters drop-off mail-in ballots in battleground state Pennsylvania
Voters drop-off mail-in ballots in battleground state Pennsylvania AFPTV / Diane DESOBEAU

At the rallies, Trump cast his struggling campaign in an optimistic light, predicting that his surprise 2016 victory over Hillary Clinton would be repeated.

"The same thing is happening," he said: "a similar result and maybe even a bigger margin."

Trump's message largely ignored the Covid-19 crisis, with infections surging nationwide, and instead focused on what he said would be a strong economic comeback.

Democratic presidential candidate Joe Biden says his events are low key to protect against spreading the coronavirus
Democratic presidential candidate Joe Biden says his events are low key to protect against spreading the coronavirus AFP / JIM WATSON

Fixing on Biden's promises to encourage a shift to renewable energies, Trump told each of the rallies in Pennsylvania -- a major natural gas producing area -- that the Democrat would "abolish the entire US oil industry."

"Biden's plan is an economic death sentence for Pennsylvania's energy sector," he said.

Clearly irked by Trump's message, Biden used his own quick appearance in Chester to insist: "I'm not shutting down oil fields, I'm not eliminating fracking. I'm investing in clean energy."

Trump also intensified his personal insults, calling Biden "sleepy" and unable to cope with foreign leaders who are "100 percent sharp."

And the former reality television performer showed his talent as entertainer with a series of exaggerated and colorful warnings about life under a Democratic presidency.

"You will have a depression the likes of which we have never seen outside, perhaps, 1929," he said, predicting that Americans would no longer have air conditioning and that the Democrats would ban cows.

Biden was in Pennsylvania Saturday and is due to campaign Thursday in Florida -- another hugely important swing state -- before trips to Iowa and Wisconsin on Friday.

But many days he is hunkered down at home doing online video talks or sending allies like popular former president Barack Obama to campaign on his behalf -- making him the most lightly traveled presidential candidate in recent history.

By contrast, Trump now flies on Air Force One to two to three big rallies a day, with a plan to ramp up to at least five in the final sprint.

Biden argues he is sticking to medical guidelines on Covid-19, while Trump, who himself was hospitalized this month with the coronavirus, regularly brings together thousands of people without masks.

"I am not over-confident about anything," Biden told reporters. "The big difference between us, and the reason it looks like we're not travelling: we're not putting on super-spreaders."