In this sense, the fight against coronavirus has the potential to define American politics the way an armed conflict might: It poses a threat to the health and safety of the public, and voters support the effort to defeat it even at a significant economic cost.

Unlike a recession — but again somewhat like a crisis or war — the emergence of coronavirus was not necessarily bad news for Mr. Trump. It offered an opportunity for nonpartisan, presidential leadership on a pressing issue that transcends traditional political divisions.

Not even a high death toll was necessarily a problem for the president’s political fortunes. Gov. Andrew Cuomo seems to have emerged with stronger ratings in New York despite tens of thousands of deaths, just as Franklin D. Roosevelt and George W. Bush emerged stronger after the catastrophic Pearl Harbor and Sept. 11 attacks. Winston Churchill presided over his troops’ defeat in France in 1940 and still claimed his place as a prominent figure in world history in the very same month.