Hackers stole $US2.3 million ($A3.3 million) from the Wisconsin Republican Party’s account that was being used to help re-elect US President Donald Trump in the key battleground state, the party’s chairman says.

The party noticed the suspicious activity on October 22 and contacted the FBI on Friday, Republican Party chairman Andrew Hitt said.

Mr Hitt said the FBI was investigating.

“There’s no doubt RPW is now at a disadvantage with that money being gone,” Hitt said.

The party and campaign needed money late in the race to make quick decisions, he said.

Mr Hitt said the hackers were able to manipulate invoices from four vendors who were being paid to send out direct mail for Mr Trump’s re-election efforts and to provide pro-Trump material such as hats that could be handed out to supporters.

Invoices were altered so when the party paid them, the money went to the hackers instead of the vendors, Mr Hitt said.

Mr Hitt said it appeared the attack began as a phishing attempt.

Mr Trump won Wisconsin by fewer than 23,000 votes in 2016 and it remains a key swing state his bid to win again on November 3

Mr Trump planned his third visit to the state in a week on Friday. His Democrat rival, Joe Biden, also planned to campaign the state on Friday.

Earlier, both candidates rallied supporters in the closely fought state of Florida, highlighting their contrasting approaches to the resurgent coronavirus pandemic.

Opinion polls show Mr Biden with a significant edge nationally but a tighter lead in battleground states that play a decisive role in the final result.

A Reuters/Ipsos poll released on Wednesday showed Mr Trump essentially moving into a tie with Mr Biden in Florida, with 49 per cent saying they would vote for Mr Biden and 47 per cent for the President.

With its 29 electoral votes, the state is a major prize in Tuesday’s election. Mr Trump’s victory in Florida in 2016 was vital to his surprise win.

Thousands of people, many without masks, crowded at an outdoor event in Tampa on Thursday to hear Mr Trump mock his opponent.

“Could you imagine losing to this guy? Could you imagine?” Mr Trump said, adding he was confident of winning a second term.

Mr Biden, in contrast, held a drive-in rally later at a college north of Miami where attendees remained in cars to avoid spread of the disease.

“Donald Trump has given up” on fighting COVID-19, he told them.

With an eye on the Latino vote in Florida, Mr Biden pushed back on a Republican argument that Mr Trump would be tougher on left-wing governments in Cuba and Venezuela.

“President Trump can’t advance democracy and human rights for the Cuban people and the Venezuelan people when he has embraced dictators around the world,” Mr Biden said.

Elsewhere, the pandemic that has upended life across the US, killed more than 227,000 people and caused millions of job losses, is roaring back.

Mr Trump has repeatedly dismissed its threat, saying his opponents and the media will stop paying attention to it after the November 3 election, even as leaders in Europe scramble to contain a second wave and health experts predict a grim US winter.

Mr Trump’s own White House coronavirus task force is warning of a persistent and broad spread of COVID-19 in the western half of the US, including in a number of states that will play an important election role.

“We are on a very difficult trajectory. We’re going in the wrong direction,” National Institute of Allergy and Infectious Diseases director Dr Anthony Fauci told CNBC on Wednesday night.

Mr Trump hailed figures on Thursday showing the US economy grew at an unrivalled annualised pace of 33 per cent in the third quarter because of a huge federal pandemic relief program.

It is doubtful, however, whether data this close to election day can influence the outcome.

Following his own bout with COVID-19, the President has had a hectic campaign schedule, holding up to three rallies a day in different states.

Mr Biden has been measured, spending two days this week close to his home base of Delaware.

In all, Mr Trump will visit 10 states in the last week of the campaign and host 11 rallies in the final 48 hours.

More than 80 million Americans have already cast ballots, setting the stage for the highest participation rate in over a century.

-with AAPhttps://thenewdaily.com.au/news/world/2020/10/30/anthony-fauci-covid-warning/