U.S. President Donald Trump on Monday returned to the campaign trail after recovering from the novel coronavirus, hoping to turn around his faltering re-election fight just weeks before the Nov. 3 presidential poll.

"Twenty-two days from now...we're going to win four more years in the White House. We're going to make our country greater than it has ever been before," the 74-year-old Republican president, who was discharged from hospital on Oct. 5, said in Florida, a key battleground state crucial for his re-election chances.

U.S. President Donald Trump attends a rally in Sanford, Florida, on Oct. 12, 2020. (UPI/Kyodo)

Not wearing a mask, Trump talked for about an hour in front of a large crowd and boasted about his immunity from the virus, which has left more than 210,000 people in the country dead -- the most of any country in the world.

"I feel so powerful," he said, "It does give you a good feeling when you can beat something and now they say 'You're immune.' I don't know for how long, some people say for life, some people say for four months."

Trump maintained an upbeat view of his election prospects during the campaign speech but he is lagging behind Democratic challenger Joe Biden, the 77-year-old former vice president, with the margin exceeding 10 percentage points, according to an average of national polling data by poll tracking website Real Clear Politics.

Biden, meanwhile, turned up the heat on Trump as he traveled to Ohio, a bellwether Midwestern state which Trump won in the previous election in 2016. Polls have showed that the two are now in a tight race in the state.

"Experts are telling us we may lose up to another 200,000 lives (due to the pandemic) by the end of January. All because the president is only worried about one thing, the stock market, because he refuses to follow science," Biden said.

His jab about Trump's indifference to science was apparently in reference to the president's often-cavalier attitude toward the highly contagious virus, including his reluctance to wear a mask.

Trump's underdog status has become clearer following the now infamous first debate with Biden on Sept. 29, which was marked by interruptions and name-calling, and the president's announcement days later that he tested positive for the virus.

After suffering a high fever and twice receiving supplemental oxygen due to his illness, the president was cleared by his physician Sean Conley on Saturday as "no longer considered a transmission risk to others."

Supporters of U.S. President Donald Trump attend a rally in Sanford, Florida, on Oct. 12, 2020. (UPI/Kyodo)

In the latest memorandum on the president's health, released just hours before the start of the rally in Florida, Conley said Trump has tested negative for the COVID-19 respiratory disease "on consecutive days."

Although Trump has been criticized over the past months for repeatedly downplaying the threat of the virus and handling the pandemic poorly, his quick recovery seems to have emboldened the president.

Trump has told the public not to be afraid of COVID-19 and tweeted Sunday, without clear evidence, that he is now "immune" from the virus, a message Twitter Inc. flagged as violating its rules about "spreading misleading and potentially harmful information" related to the disease.

While the coronavirus pandemic and the economy are seen to be key issues for voters, Trump and the Republicans have also been rushing for Senate confirmation of the president's pick to fill the Supreme Court vacancy created by the death of liberal icon, justice Ruth Bader Ginsburg.

The Democrats have said a new justice, which is a lifetime appointment, should be approved after voters have had their say on who should lead the country following the Nov. 3 election.

But hearings for conservative judge Amy Barrett started Monday at the Judiciary Committee of the Republican-controlled Senate, with the Republicans eyeing a final confirmation vote in the chamber before the election.

Barrett's presence in the Supreme Court would solidify a conservative majority on the nine-member bench, which is tasked with ruling on crucial issues such as abortion, health care and possibly legal challenges over contested election results.