We are going through a kind of referendum on Donald Trump’s future. Resolving that would be better left to voters than to an attorney general already distrusted by about half the population.

In an unusual burst of self-awareness Monday, Mr. Trump told Fox News Digital: “Whatever we can do to help because the temperature has to be brought down in the country. If it isn’t, terrible things are going to happen.”

During his tumultuous presidency, Mr. Trump sometimes said his opponents, not least the media, loved him because he fed their political and economic interests. And his own.

Political retribution has become a business model. On its current, indeterminate course, the Mar-a-Lago investigation is pushing the American politics back to obsessing over Mr. Trump and his endless enemies, such as the primary-election defeat of his Inspector Javert, Wyoming Rep. Liz Cheney.

A belief seems to exist in some quarters that the U.S.’s appetite and capacity for political rancor is limitless. It is not. What may be good for Donald Trump’s presidential prospects or his cynical adversaries if the Justice Department’s Mar-a-Lago investigation smolders indefinitely will not be good for a country already in extremis.