In other words: By firing Comey and then tweeting recklessly about it, Trump elevated a long-running but manageable problem—the so-called “Russia thing”—into an independent investigation that seriously endangers his presidency.

I call the Russia thing a manageable problem because, almost a year after the FBI launched the counterintelligence probe, no serious allegation of wrongdoing by Americans has been made. Indeed, the investigation seems to be headed in directions having little to do with Russia’s hacking of Democratic emails and election systems. Flynn’s troubles involve his statements to the FBI and his work for the government of Turkey. The question for former Trump campaign manager Paul Manafort is whether he properly reported income made overseas. Senior adviser and Trump-in-law Jared Kushner is under the microscope for a meeting he had during the transition with a Russian banker who has a relationship with Vladimir Putin.

If President Trump had let the investigation develop as other presidents have done in the past, it seems unlikely to have reached him. This is especially the case now that we know that Comey had informed the president on multiple occasions that he was not a subject of the inquiry, that Comey, while disturbed by his encounters with Trump, did not see them as warranting his resignation, and that no one other than Trump ever told him to drop the Flynn inquiry.

But Donald Trump, as we know, is not like other presidents. He couldn’t let it rest.