The 25th Amendment to the U.S. Constitution outlines a procedure by which the Vice President of the United States can assume the powers of the presidency if the sitting president becomes incapacitated. Given the severity of COVID-19, especially for older people, it is entirely possible that the disease could render 74 year-old Trump unable to perform his duties.

Basically, as outlined by the New York Times, the president could voluntarily hand over authority to Vice President Mike Pence on a temporary basis. Otherwise, a majority of the president's cabinet members and (if Trump challenges the move) two-thirds of both Houses of Congress could approve of a measure to temporarily remove Trump from office and allow Pence to assume duties as acting president.

As outlined by Business Insider, there have been three times when presidents have briefly handed over power voluntarily due to health emergencies, but never an instance when the president has been involuntarily removed using the procedure of the amendment. Pence has generally defended the President on major policy issues, and he would likely continue much of the Trump administration's agenda if he assumed the role of acting president.

President Trump likely contracted COVID-19 from close aide Hope Hicks, who has often been in close proximity with the president while neither wore face masks or practiced social distancing. In general, the president and his aides and advisors have rarely practiced recommended guidelines for avoiding COVID-19 infection. This raises the possibility that many more officials and staff within the White House could have contracted the coronavirus. Republican National Committee Chairwoman Ronna McDaniel, who was in close contact with the president last week, has also tested positive for COVID-19, reports the New York Times.

Vice President Pence announced Friday morning that he and his wife Karen had tested negative for the virus. Nevertheless, Trump and Pence often interact without wearing masks or social distancing, and the two appeared together as recently as Monday. It can take up to 14 days after exposure for individuals infected by the coronavirus to test positive, meaning that Pence is not out of the woods yet. 

Should both Trump and Pence be incapacitated by COVID-19, the Presidential Succession Act of 1947 specifies that the Speaker of the House, currently Democratic Representative Nancy Pelosi, would be next in line to become president. Pelosi and Trump have constantly clashed over the last 3 1/2 years, and Pelosi even gleefully led impeachment proceedings against Trump.  A President Pelosi and a Democratic-controlled House of Representatives would be limited by a Republican-majority Senate. Nevertheless, Pelosi could potentially slow down or halt some of Trump's agenda, such as by rescinding or altering the many executive orders that Trump has issued during his presidency.

CNN reports that Democratic presidential candidate Joe Biden and his wife Jill tested negative for COVID-19 on Friday. But Biden having shared a stage with a frequently disruptive President Trump during Tuesday's messy presidential debate raises the fear that Biden could have been exposed to the coronavirus as well. Such exposure might not show up on tests for another week or more. Currently, the Biden campaign has indicated that the former vice president will continue campaigning as normal. But should Biden later test positive, this would disrupt his campaign, which has already been heavily criticized by Republicans for sticking Biden in a "basement."

Biden's strategy of actually listening to health experts seems very smart right about now, but a positive test for Biden could give Republicans fuel for arguing that following the rules didn't protect him. Of course, it wouldn't make much logical sense for Republicans to continue their criticisms of Biden while their own candidate quarantines, but logic and consistency have not constrained the Republican Party in recent years, and it is unlikely that it will give up on hypocrisy this close to the election. And the 77-year-old Biden, like Trump, falls into one of the age brackets at highest risk of developing severe complications from COVID-19, creating a danger to the former vice president's health if his encounter with Trump really did expose him to the virus.

If Trump develops a severe illness from COVID-19 that puts his long-term recovery in doubt (or worse), there may be pressure to remove him from the ballot. Pence would likely assume the role of Republican nominee. The rules of the Republican National Committee allow the party to make such a change, but, as explained in an article by Quartz, the deadline to do so may have already passed. The Democrats could similarly swap out Biden for Harris or even another nominee if they needed to do so. However, given that millions have already voted or are doing so now via mail-in ballots, such a last-minute change, even if possible, could potentially wreak havoc on the election. 

In the end, as Yahoo News reports, it would likely be up to the individual state governments and/or members of the Electoral College to decide how to count votes that were cast for Trump or Biden if these men were no longer in the race. The Electoral College has been heavily criticized, especially in 2000 and 2016 when the winners of the popular vote nonetheless loss the elections. Having the Electoral College decide how to reallocate votes in November creates the potential for an unpredictable and potentially controversial outcome. Such an outcome could end up being challenged in the Supreme Court, which would be equally controversial given the partisan leaning of the body and the likelihood of Judge Amy Coney Barrett's divisive nomination being approved by then.

Trump's diagnosis caps what has been a disastrous week for the president.

Since Tuesday's messy and embarrassing presidential debate, Trump has been deflecting criticisms from both parties over his performance. His rude, unhinged approach to the debate has been called unpresidential and shameful by opponents and pundits, and even many of his allies saw it as a missed opportunity. Meanwhile, his refusal to denounce white supremacists and seemingly endorse the Proud Boys have been widely condemned.  

But now, as Trump faces a health crisis that could see him battling for his life, there is a possibility that he will draw sympathy from the American public. His supporters may see this as a time to rally around their president. Some may even make the calculation that, even if the president takes a turn for the worse, this would leave staunch conservative Pence in charge. 

Even some moderates may be willing to give the president the benefit of the doubt while he's facing a major life crisis. And Democrats could be lulled into a false sense of complacency, thinking that this news will help them win and thus not showing up to the polls in large enough numbers to secure an electoral victory. Such apathy may have cost former Secretary of State Hillary Clinton the election in 2016, and could do again with Biden in November.

It's been clear for most of the year that the COVID-19 pandemic would be the major issue of this year's election. The United States' leading death toll with its number of cases and the economic collapse caused by the disease and related shutdowns have all brought severe criticism to the Trump administration. The pandemic wiped out much of the economic gains made during Trump's first term, heightened racial disparities in healthcare and the economy, and generally called into question the President's integrity and leadership style.

Meanwhile, Trump has consistently downplayed or even lied about the crisis. He's had multiple reasons for doing so: wanting to paint a rosy picture of his record in order to win re-election, desiring to appear strong and decisive, and a pathological unwillingness to admit to his mistakes. 

But it's very hard to make the argument that the President's approach to COVID-19 has ben a success when he could not even prevent himself and his wife from contracting the disease. His diagnosis jabs a huge hole into the beliefs of Trump supporters who argue that the pandemic is a hoax designed to damage his presidency. And his attempts to present himself as strong and unafraid by not wearing a mask appear to be foolish now that he has contracted a disease that his own experts have been saying is avoidable if proper procedures are followed. 

The president's own diagnosis is perhaps the most compelling piece of evidence for all the criticisms that have been levied against him. The New York Times reports that one Republican strategist has said that "it’s hard to imagine this doesn’t end [Trump's] hopes of re-election."

In the end, the president's own personal recklessness may well have made the strongest case possible against a second Trump term.