News reports from BBC and CNN indicate that the likely vector of infection was presidential aide Hope Hicks who travelled with the presidential party aboard AF1 both to and back from the presidential debate in Ohio on Tuesday night.
https://www.bbc.co.uk/news/world-us-canada-54381848News that Hope Hicks had been taken ill on Wednesday, and subsequently tested positive for COVID-19 on Thursday was apparently leaked to the press, which rather forced today’s disclosure about the POTUS and his wife.
The president’s physician Dr. Sean Conley has issued a statement saying that the president is well and continuing with his duties while in quarantine - but there hasn’t been any statement on whether the VP Mike Pence has tested either negative or positive for COVID-19 since the president’s result was confirmed.
President Trump, who is 74 years old and obese according to his most recent medicals, is in a higher risk group of COVID-19 patients. He is five times more likely to require hospiital treatment, and up to ninety times more likely to die if his condition deteriorates to the point where he requires ICU treatment.
Todays news changes both the trajectory of the presidential election, and the calculus of power in no uncertain manner.
i. If president Trump and vice-president Mike Pence both became too ill to continue with their duties, then under the succession protocols, the powers of the presidency would pass to the Speaker of the House - which is Democratic leader Nancy Pelosi.
ii. The president won’t be able to carry on with campaign rallies or any more presidential debates whilst in quarantine which will last for at least another 10 days. Given that there are only 33 days left until the election, this is will have a considerable influence on polling trends and vote swings.
iii. If the president dies, or remains critically ill to the point where the 25th Amendment is in play because he is incapacitated, then the GOP would be forced to nominate a replacement presidental candidate just before an election. This has never previously happened, and there are no precedents to follow.
Probably the nearest one was the death of William Henry Harrison who became the 9th president of the USA in 1840, but reportedly caught pneumonia while attending his own inauguration in bitterly cold weather on the 4th March, and died just 31 days later on 4th April 1841.
William Harrison was the first victim of what became known as ‘The Curse of Tippecanoe’ - A sequence of presidents who all died in office after being elected in years evenly divisble by 20, or that ended in a zero. The curse was supposedly laid by a native american medicine man after a tribal leader was killed in an Indian war in which Harrison was the commander.
https://en.wikipedia.org/wiki/Curse_of_TippecanoeThe list included William Harrison (1840), Abraham Lincoln (1860), James Garfield (1880), William Mckinley (1900), Warren Harding (1920), Franklin D. Roosevelt (1940) and John F. Kennedy (1960). Ronald Reagan who was elected in 1980 is one POTUS to have bucked this trend. He was shot in an assassination attempt in 1981, but survived.
ETA - G.W Bush was also elected in 2000 and survived.