With the economy faltering and the political landscape unsettled as the coronavirus death toll climbs, a stark and unavoidable question now confronts President Trump and his advisers: Can he save his campaign for re-election when so much is suddenly going so wrong?

After three years of Republicans’ championing signs of financial prosperity that were to be Mr. Trump’s chief re-election argument, the president has never needed a new message to voters as he does now, not to mention luck. At this point, the president has one clear option for how to proceed politically, and is hoping that an array of factors will break his way.

The option, which he has brazenly pushed in recent days, is to cast himself as a “wartime president” who looks in charge of a nation under siege while his likely Democratic opponent, former Vice President Joseph R. Biden Jr., is largely out of sight hunkered down in Delaware. This gambit, however, requires a rewriting of history—Mr. Trump’s muted approach to the virus early on—and it’s far from clear if many voters will accept the idea of him as a wartime leader.