While Democratic presidential nominee Joe Biden heads to the crucial battleground state of Florida on Monday, President Trump is hospitalized at Walter Reed National Military Medical Center after being diagnosed with COVID-19.

After months of mocking the former vice president for his light in-person campaign schedule amid the coronavirus pandemic and ridiculing him for "hiding in his basement” at his home in Delaware, it’s now Trump who is sidelined and forced to postpone events, with a month to go until Election Day on Nov. 3, and with millions of Americans already casting absentee ballots or early voting at polling stations.

LIVE UPDATES FROM FOX NEWS ON TRUMP'S HOSPITALIZATION FOR CORONAVIRUS

And with the clock ticking -- and the president trailing Biden in the latest public opinion polls in many of the key battleground states that will decide the White House winner -- the spotlight in the presidential election has dramatically shifted once again.

Just two weeks after the death of trailblazing Supreme Court Justice Ruth Bader Ginsburg rocked the race for the White House, giving the president an opportunity to rally Republicans by moving to quickly confirm a conservative justice to succeed the liberal-leaning Ginsburg on the high court, the focus of the campaign has been upended again.

President Donald Trump arrives at Walter Reed National Military Medical Center, in Bethesda, Md., Friday, Oct. 2, 2020, on Marine One helicopter after he tested positive for COVID-19. White House chief of staff Mark Meadows is at second from left. (AP Photo/Jacquelyn Martin)

The president’s confirmation early Friday morning that he and first lady Melania Trump had tested positive for COVID-19 instantly put the focus of the White House race firmly back on the coronavirus and the Trump administration's efforts to fight the pandemic. That was further heightened hours later when Trump was admitted to Walter Reed.

“It’s not good news for the president in that the focus is now going to be on Covid-19, and when the focus is on Covid-19 Biden has a 10, 11, 12-point advantage,” veteran Republican pollster and communications consultant Frank Luntz said on Fox News’ “The Daily Briefing with Dana Perino.”

Luntz stressed that “the economy is Donald Trump’s strength, and the fact that he can’t get out there now is going to be a challenge for the campaign.”

"Fox News Sunday" anchor Chris Wallace agreed that “the coronavirus and the president’s handling of it is going to the top of the agenda.”

Wallace, who moderated Tuesday’s first presidential debate between Biden and Trump, spotlighted on "America’s Newsroom” that the pandemic “becomes the most important issue. … The general feeling on some peoples’ part is that the president hasn’t been cautious enough and that Biden has been too cautious. That’s going to be an issue now going forward.”

The pandemic swept the nation in February and March. Two weeks ago, the nation passed another grim milestone, as more than 200,000 COVID-19-related deaths were recorded, with than 7 million infections confirmed across the country.

Over the past seven months, Biden has repeatedly criticized the president -- charging Trump initially downplayed the severity of the outbreak and then botched the federal government’s response. Trump and his campaign have repeatedly pushed back on such criticism, citing among other things the administration's early effort to restrict air travel with China, where the pandemic originated.

BIDEN SAYS TRUMP'S COVID DIAGNOSIS REMINDER 'WE HAVE TO TAKE THIS VIRUS SERIOUSLY'

Hours before the president was hospitalized, Biden was out on the campaign trail, speaking in the key swing state of Michigan. He curtailed his criticism of Trump – and his campaign later highlighted that they were pulling all negative ads. But the former vice president emphasized that Trump’s coronavirus diagnosis “is a bracing reminder to all of us that we have to take this virus seriously. It’s not going away automatically….The news is a reminder that we as a nation need to do better in dealing with this pandemic.”

Democratic presidential candidate former Vice President Joe Biden arrives to speak at United Food & Commercial Workers Union Local 951 in Grand Rapids, Mich., Friday, Oct. 2, 2020. (AP Photo/Andrew Harnik)

Biden’s comments came three days after Trump – who avoided wearing a mask in public until July and who continues to resist any forceful urging of Americans to wear masks -- once again mocked Biden for wearing a mask, saying at Tuesday’s debate that “I don’t wear a mask like him. Every time you see him, he’s got a mask. He could be speaking 200 feet away and he shows up with the biggest mask I’ve ever seen.”

Biden – who’s called for mask mandates across the country – on Friday reupped his pitch as he called for “mandates nationwide.”

And he urged Americans to “be patriotic. It’s not about being a tough guy. It’s about doing your part. Wearing a mask is not only going to protect you, but it also protects those around you. Your mom, your dad, your brother, sister, husband, wife, neighbor, co-worker. Don’t just do it for yourself.”

The president’s condition now makes it extremely hard for him to make the case – that he’s repeatedly argued in recent weeks – that “we’re turning the corner” on the battle against the outbreak and that it’s time to reopen the economy.

Mo Elleithee, the founding executive director of Georgetown University's Institute of Politics and Public Service and a Fox News contributor, said the news complicates things for the Trump campaign, which he noted “has tried to focus on the debate on everything but COVID, and when they do talk about it, they’ve tried to argue that the response has been effective. It will be much harder for them to do either of those things now.”

WHO'S MORE TRUSTED TO HANDLE CORONAVIRUS - BIDEN OR TRUMP?

Biden holds a firm lead over Trump when it comes to coronavirus polling. The most recent national poll by Fox News indicated that by a 52%-44% margin, voters trusted the former vice president more than the president to do a better job handling the crisis.

Elleithee, a senior spokesman for Hillary Clinton’s 2008 presidential campaign who later served as communications director for the Democratic National Committee, said, “The question is whether or not this serves as a wakeup call for those who don’t take COVID seriously.  It will be a lot harder for people to downplay it now, and ensures that COVID will continue to be the number one issue on everyone’s mind. If this disease can work its way into the Oval Office, it’s further proof that anyone can get it, raising the stakes in the debate over the government’s response.”

For the president and his campaign – the bad news didn’t end with his coronavirus diagnosis. Two key players in the combined forces of the president’s re-election team and the Republican National Committee (RNC) also tested positive for COVID-19 – Trump campaign manager Bill Stepien and RNC chair Ronna McDaniel.

Trump debate coach and former New Jersey Gov. Chris Christie on Saturday was also hospitalized after testing positive.

And the two remaining presidential debates – scheduled for Oct. 15 and 22 – are now very much up in the air – potentially robbing Trump of his last remaining opportunities to move the needle in the White House race.

TRUMP CAMPAIGN STEPS UP DIGITAL PRESENCE ON SUNDAY

For now, with Trump sidelined, his campaign will rely on Vice President Mike Pence and other surrogates to try and pick up the pace.

But Luntz sees a possible silver lining in the president’s hospitalization.

“I believe that he should make a statement to the public as (British prime minister) Boris Johnson did after he got sick and it’s a chance for him to say, 'here’s what we’re going to do, here’s what we’ve done and here’s what we will be doing over the coming days, weeks and months,' for him to be empathetic.”

Luntz noted that “the president’s basically six and a half to seven points behind with just 30 days to go, so I think he needs to use this as an opportunity to reframe, reshape, and communicate to the public what he did so effectively four years ago.”