If the sell-off continues, it could undermine a key pillar of the president’s re-election pitch. That might be less of an issue if Mr. Trump had not so frequently spoken of the stock market as a real-time barometer of his presidency’s success.

But there’s more at stake than public relations. There’s also the risk that the administration’s focus on the optics of the market distracts them from the bigger task at hand — trying to protect against the potential spread of disease and loss of life that would accompany a global pandemic.

Ideally, even economic officials who don’t have expertise in disease transmission would spend their time trying to understand what industries are likely to be heavily affected and whether government can do anything to help them work through the supply chain disruptions and other bad effects of the virus.

Tuesday afternoon, the chief White House economic adviser, Larry Kudlow, was interviewed on CNBC in the midst of the sell-off, and focused on talking up the markets.

“The virus story is not going to last forever,” he said on “The Exchange.” “To me, if you are an investor out there and you have a long-term point of view, I would suggest very seriously taking a look at the market; the stock market, that is a lot cheaper than it was a week or two ago.”