Federal Reserve chairman Jay Powell and his colleagues made the right call in cutting the federal funds rate by 50 basis points. They knew full well what the naysayers would claim: A rate cut is an overreaction; it can’t conjure a coronavirus vaccine into being; the central bank will have little ammunition left when it really needs some. It’s a good thing they ignored all of that.

It’s true that the Fed cannot stop the coronavirus from harming the supply side of the economy. It can’t rescue the travel industry or make up for lost work days. What it can do is prevent a supply-side hit from generating an additional demand-side one. . . .