It is impossible to know how Mr. Trump’s own behavior and calculations would have been different if he had been greeted with the usual presidential honeymoon rather than a concerted campaign to portray him as a Russian stooge.

But one judgment we are ready to render on Mr. Comey’s tenure: If he had chosen a different career (say, driving instructor) and never joined the FBI, I doubt we’d be lamenting his absence now. Indeed, it seems overwhelmingly likely that the country would be better off today without his heedless and ill-advised decisions.

A precedent from U.S. history doesn’t leap to mind but one from popular culture does: Maxwell Smart, the bumbling master spy with the inflated ego and talent for disaster from the TV show “Get Smart.” As Mel Brooks, creator of the rollicking 1960s sitcom, told a reporter at the time, “No one had ever done a show about an idiot before. I decided to be the first.”