Biden, who tested negative on Friday, three days after debating Trump, has repeatedly wished the president a speedy recovery. But the former vice president and his aides have used his Republican rival's positive test to underline a consistent campaign message: Biden would handle the pandemic better than Trump.

Deputy campaign manager Kate Bedingfield said on Sunday that Biden would keep making that case for the remaining 30 days of the campaign.

"It's a choice between two different styles of leadership and since the virus came to our shores back in the spring, Joe Biden has led by example," she told ABC's "This Week," citing the campaign's use of masks, social distancing and limits on the number of people at campaign events.

The United States has recorded 7.4 million coronavirus infections and more than 209,000 deaths in the pandemic, more than any other country. Trump briefly had an opportunity to pivot the public's focus away from COVID-19 when the death last month of Supreme Court Justice Ruth Bader Ginsburg gave him the chance to nominate a third lifetime appointment to the top court, before his own illness returned the spotlight to the disease.

With Trump, 74, sidelined from public events as he fights the virus, his campaign has begun describing him as a "warrior" in messages to supporters that call for donations. Aides have continued to criticize Biden's cautious approach to the virus.

Jason Miller, a Trump campaign senior adviser, mocked Biden on Sunday for consistently wearing a face mask, saying the 77-year-old Democratic presidential nominee was using masks "as a prop."

"We can't all just stay in our basement for the rest of our lives," Miller told "This Week."

Voters could judge harshly an approach that continues to downplay the seriousness of the virus, said Kelly Dietrich, a Democratic strategist and founder of the National Democratic Training Committee, a group that trains party candidates.

"This has touched every American's life," he said.

On Monday, Biden and his wife, Jill, are scheduled to resume in-person campaigning in Florida, where opinion polls show a tight race for the state's crucial 29 electoral college votes. Biden will talk to Hispanic voters about his plan to rebuild the US economy after the coronavirus, his campaign said.

More than 3.3 million ballots had already been cast nationwide by Sunday, according to the Elections Project at the University of Florida - as more Americans vote early or by mail to avoid being exposed to the virus at crowded polling places on Election Day.

A Reuters/Ipsos poll taken Friday and Saturday after the president tested positive for the coronavirus, found Biden leading Trump by 10 percentage points nationally and that nearly two-thirds of Americans thought that Trump probably would not have been infected if he had taken the virus more seriously.

As Trump's doctors and aides gave sometimes unclear messages about the president's health situation over the weekend, Biden's campaign said it would publish the results of every COVID-19 test the candidate takes. Biden was set to be tested on Sunday morning, campaign officials said, but no results had been announced as of Sunday afternoon.

Biden would not need to do much to benefit from Trump's diagnosis, since many Americans already viewed Trump's approach to the virus as cavalier, said David Greenberg, a historian at Rutgers University.

"They're going to think that even more now, so I don't think Biden needs to hammer that home too hard," he said.

It remains uncertain when Trump will return to the campaign trail, if at all, and whether he will be able to participate in the second presidential debate on Oct. 15.