No one was surprised when President Trump called Stormy Daniels "Horseface" on Twitter. After all, this is the man who called Hillary Clinton "a nasty woman," Arianna Huffington "a dog," Bette Midler "an extremely unattractive woman," and Rosie O'Donnell a "disgusting pig" with a "fat, ugly face."

The only shocking thing about Trump's "Horseface" tweet was how unshocking it was. We know he sleeps with porn stars, disparages women's looks, and can't spell "horse face" properly. We know we're supposed to be shocked by these things, but it's hard to remain shocked when you're shocked all the time — not just daily, but hourly. It's shocking when good people do bad things, not when bad people do bad things.

After a rumor spread that there might be a tape of Trump saying the N-word, people were more surprised by the absence of the tape than by the rumor itself. Of course Trump said the N-word was the operating premise.

Regarding The New York Times' investigation into the dubious tax schemes of Trump's family over decades, almost no one cared. The story was, as Politico's Jack Shafer put it, a bombshell that bombed. It bombed because it was predictable. It's not a surprise when a newspaper finds out that a guy who won't release his tax returns has a shady reason for keeping them secret.

A man who cheats on his taxes is liable to cheat on his wives. If this man cheats on his first wife, as Trump did, he might cheat on his second and third. While married to his first wife, Trump said his primary concern in life was a "beautiful piece of ass." While married to his second wife, he said that he "could have" had sex with Princess Diana were it not for her untimely death just weeks earlier.

Is anyone surprised that multiple women claim that Trump sexually assaulted them when he himself bragged on tape of sexually assaulting women? Not even his supporters are.

It is not surprising that a person unfamiliar with Frederick Douglass and the nuclear triad is unfamiliar with lots of other things. Nor is it surprising that Trump, who two years ago thought judges signed bills, is constitutionally illiterate, not to mention almost literally illiterate. What would be surprising is if Trump went on Are You Smarter Than a 5th Grader? and won.

We are surprised when we aren't appalled, not when we are. We are shocked only when we aren't shocked. When Trump gives a speech without calling the media "the enemy of the people," without bragging about the size of his crowds, without lying flagrantly and repeatedly, and without praising dictators or defending sex predators, we are stunned and impressed. After Trump's first speech to a joint session of Congress, in which he paid tribute to the widow of a Navy SEAL, CNN's Van Jones remarked, "He became president of the United States in that moment, period ... That was one of the most extraordinary moments you have ever seen in American politics." Trump's utterly conventional speech seemed extraordinary and historic at the time — and it was — but only because of our dismally low expectations of the man delivering it.

This is the key to his (limited) success. He benefits from — indeed, thrives on — our low expectations of him. No Trump scandal will ever truly shock us, which is why no scandal will ever dethrone him.

Many people in the know expect Special Counsel Robert Mueller's report to show ample evidence of collusion, financial crimes, and possibly worse. If the report is as bad as they predict, it will, by definition, not be shocking. The worst is what we expect from Trump, because that's usually what he gives us.

We know, based on decades of evidence, that Trump is a bad person, and so it's not surprising when he behaves like one. We know, based on 21 months of experience, that he is unfit to be president, and so we are not surprised when he proves us right. Trump can horrify us, annoy us, embarrass us — but he cannot shock us. We know him too well.

The only thing Trump can do to shock us is to behave like a grownup for a sustained period of time, without the aid of sedatives. For Trump, this is an impossible task. He can do adultery, but not adulthood.