By now, most people are familiar with the president’s habit of slagging the physical, mental and moral fitness of his detractors. From “Crooked Hillary” Clinton to “Psycho Joe” Scarborough to “low energy” Jeb Bush to “crazy,” “unhinged,” “low IQ” Maxine Waters — Mr. Trump adheres to the belief that, if you’re going to go low, you should get as personal and elemental as possible.

This weekend provided a particularly redolent example, as the president, perhaps still vibrating from his overconsumption of the Sunday news shows, hit back at a bit of displeasing commentary by Democratic Representative Adam Schiff, with this scatological twit fit:

[Tweet]  So funny to see little Adam Schitt (D-CA) talking about the fact that Acting Attorney General Matt Whitaker was not approved by the Senate, but not mentioning the fact that Bob Mueller (who is highly conflicted) was not approved by the Senate!

Quicker than you can say “White House decorum,” Mr. Trump’s remarks became the talk of social media. Did the president really just call the incoming chairman of the House Intelligence Committee that? If it was a typo, he didn’t bother to delete the tweet and correct it, as he often does. In any case, doesn’t Mr. Trump realize how childish he sounds? How rude? How unpresidential?

Trolling the libs with serial outrages — just for, one might say, schiffs and giggles — is a source of endless delight for Mr. Trump. It is also central to his survival strategy: The president burnishes the swaggering, politically incorrect persona that thrills his base, even as he siphons attention away from the substance of the real outrages that his administration is perpetrating on a near-daily basis. Who has time to focus on the finer points of trade policy or prescription drug costs or the continuing assault on democratic institutions when the leader of the free world is tweeting bathroom humor?

This is how Mr. Trump rolls. And if you think he has been over-the-top while his Republican enablers have controlled all of Congress, just wait until the Democrats take over the House in January. This president has repeatedly made clear that he considers himself above the law and accountable to no one. He is unlikely to greet Democratic efforts at oversight with any sort of restraint. Expect the nicknames to get nastier and the attacks more gratuitous.