No modern president has publicly endured a health crisis this close to a re-election attempt. Ronald Reagan was shot and convalesced in 1981, just over two months after he was first sworn in. And Dwight D. Eisenhower suffered a heart attack while in office, but it was more than a year before he faced the voters for a second time.
Some Republicans hoped his ill-fated June rally in Tulsa, Okla., when he couldn’t come close to filling the arena and some of his own staff members got the virus, would serve as a wake-up call.
But while the event put an end to his rallies for a period, it did not make Mr. Trump more sober about the threat of the virus.
The president restarted the rallies during the Democratic convention in August. The events have been mostly, but not always, outdoors, often in hangars at smaller airfields. Yet his supporters, journalists, White House staff members, security workers and others are around one another for hours at the rallies. And many of those who attend, including Mr. Trump and members of his staff, do not wear masks.
Mr. Trump’s stance on masks has put him out of step with the majority of the country and even some in his party. Forty percent of Republicans said in a New York Times/Siena College poll last month that they supported a nationwide mask mandate when social distancing is not possible.
Other G.O.P. leaders, including Senator Mitch McConnell of Kentucky, the majority leader, have repeatedly highlighted the importance of masks and have been careful to wear them inside the Capitol.
The Times survey, along with ones taken in battleground states, also indicated that a majority of voters disapproved of Mr. Trump’s approach to the pandemic and trusted Mr. Biden to do a better job handling the situation.
This drumbeat of data has not changed Mr. Trump’s approach to the disease, though.
On Tuesday, at his first debate with Mr. Biden, Mr. Trump ridiculed his opponent, a fellow septuagenarian, for his precautions.