WASHINGTON - News that United States President Donald Trump and First Lady Melania Trump have tested positive for Covid-19 has made what was an already surreal contest even more unpredictable.

Politicians, pundits and constitutional lawyers are scrambling to find an answer to the question: What happens if a presidential candidate is incapacitated, or worse dies , before the election?

The short answer is that a messy election could get even more chaotic.

That is because while the contest is officially supposed to be held on Nov 3, voting is already underway, and replacing a candidate with the clock running down could be a legal and logistical nightmare.

There have been concerns for both Mr Trump, 74, and his presidential rival Mr Joe Biden, 77, due to their advanced age.

Less than 48 hours before his diagnosis, the President shared a stage with Mr Biden at the first presidential debate in Cleveland, Ohio - though they did not shake hands.

Mr Trump is supposedly in very good health but his party must prepare for the eventuality that it may have to field another candidate.

Dr Richard H. Pildes, professor of Constitutional Law at New York University, was asked about this very scenario in August. He said the ball would be in the hands of the candidate's political party.

Vice-President Mike Pence, who would become president in the event of Mr Trump's death, would be a top choice for the Republican Party - but not the certain pick.

The Republican National Committee (RNC) has 168 members - three from each state plus three from six territories. A vote will have to be held. The parties would then have to replace the name of their deceased candidate with that of the new candidate.

"Depending on when this happens, that might not be simple," Dr Pildes said.

"Different states have different deadlines for when the parties must certify their candidates for the ballot."

Also, if states do not have laws that permit changing the candidate's name, any change may be challenged in court - although courts would be unlikely to refuse the new nomination if the party process has been followed.

But the wrangling could delay the process.

Separately Prof Rick Hasen, professor of Law and Political Science at the University of California at Irvine, writes: "The problem here is that ballots are already out and millions of people have already voted.

At this point, it seems impossible for candidates to come up with a new name to replace a name on the ballot without starting the whole election process over, which is not possible in the 30-plus days before election day. Congress could pass a Bill delaying the election but I find it hard to believe it would do so."

The other question, if President Trump gets replaced by another candidate, is what happens to the votes that have already been cast in his favour?

In the case of some states, and Americans overseas, where early voting is already taking place by mail, it is up to individual states to review their laws and decide whether, if the candidate passes away in the interim, the ballots would automatically count towards the new candidate from his party, or be cancelled.

The verdict on that may well have to be decided in the courts.

This is because the American election is really 50 elections plus one (in the District of Columbia) with each state having its own rules and regulations.

One thing is almost certain: With the President and the First Lady in quarantine, the second presidential debate due for Oct 15 will be cancelled.

Foreign policy decisions that have been largely the turf of the White House during the Trump administration may also be placed on hold.

And if the President does succumb to the virus - regardless of the process for a substitute candidate - there is a risk of real turmoil in a deeply divided country with an economy and a people staggering under a colossal coronavirus death toll of over 200,000.