The great unknown, of course — and the tremendous risk to Mr. Trump’s political fate, no matter what he says or does — is that the human cost, the economic toll, and the longevity and course of the pandemic are all X factors that will most likely play out for months and could be strongly salient if not severe by the time of the November general election.

In perhaps the best-case scenario for Mr. Trump, the patina of a “wartime president” could prove to be influential with casual voters who don’t dig into the details of his belated response to the coronavirus, which included dismissing the threat as a Democratic “hoax” and contributing to a slow start in testing for the virus.

“He is counting on people being so traumatized on a day-to-day basis that they will forget his inaction,” said Douglas Brinkley, a professor of history at Rice University. “It’s better for him to be a wartime commander in chief than someone who, when the big crisis hit, misread it completely.”

Politically, Mr. Brinkley said, the new posture made sense. “He can claim credit for the curve flattening at some point,” he said, “and hope people will be afraid to push a leader out of office if the crisis pushes into the fall.”