The tension of the day was reflected on Air Force One as it made its way back to Washington from Florida. Representative Matt Gaetz, Republican of Florida, boarded the plane steps behind the president in Orlando, where Mr. Trump held a campaign fund-raiser, only to learn shortly after takeoff that he had been in contact with an infected person at a conservative conference late last month. He then essentially quarantined himself in the air, sitting alone in a compartment of the plane.
As the jet raced toward Washington, its television screens were tuned to Fox News showing the slow-motion progress of a cruise ship with 21 infected passengers heading to a port in Oakland, Calif., followed by overhead cameras under a “Virus Ship Watch” chyron, while a red box in the lower-left-hand corner showed the sinking Dow Jones industrial average, which finished the day down more than 2,000 points, or about 7 percent.
Mr. Trump, who regularly invokes the market as an indicator of his success, on Twitter initially blamed the meltdown on falling oil prices and the news media even though most market analysts attributed the bulk of it to concern about the effect of the virus on the global economy. He made no mention of it when he met with reporters in the evening.
He did praise his own decision last month to restrict entry to the United States by foreign citizens who had been to China in the previous 14 days.
“The big decision was early when we shut down our borders,” he said, overstating the action he took. “We were the first ones ever to do that. We’ve never done that in our country before. We would have a situation that would be a lot more dire.”
Mr. Trump has resisted canceling campaign rallies despite other large events being scrubbed, and a campaign aide said he would announce another one on Tuesday. But his campaign on Monday called off a “Women for Trump” bus tour featuring his daughter-in-law, Lara Trump, and other top election surrogates, including Mercedes Schlapp, whose husband oversees the Conservative Political Action Conference, after which an attendee tested positive for the virus.
That attendee came into contact with Mr. Meadows, Mr. Gaetz and at least three other Republican lawmakers who have now quarantined themselves.