Your high school English teacher probably taught you that one of the key elements of drama is change. The protagonist of a novel almost always emerges different at the end than she was at the beginning: She grows, she learns, she discovers her weaknesses and overcomes them, she finds the courage she didn't know she had. Without that change, stories are usually flatter and less interesting.

That's not how it works in real life, however, and the main character in our current national story — one Donald J. Trump — is uniquely immune to growth and change. Which means that it isn't hard to predict what he's going to do in any given situation. Over the next three years, President Trump will continue to amaze you. But he will never surprise you.

Yet when he does something like give a semi-tacit endorsement to the repellent Roy Moore, people still act as though they weren't expecting it. That seems to be because they persist in believing that Trump will at some point bow to political rationality or do something out of character. And he might — for a while, or for as long as his aides can hold him back. But eventually, the real Trump inevitably emerges.

So while Republicans have been tying themselves in knots figuring out how to deal with Moore, their party's nominee for a Senate seat in Alabama who has been credibly accused by eight women of pursuing or even assaulting them when they were teenagers, the White House was gingerly trying to thread a needle of not endorsing Moore, but not not endorsing him either. They obviously want to hold on to the seat, but they don't want to be associated with an accused child molester.

But Trump finally just came out and said that we can't let a Democrat win, and as for the copious and corroborated allegations against Moore, "Let me just tell you, Roy Moore denies it. That's all I can say. He denies it. And, by the way, he totally denies it." Case closed.

That's an appealing standard for a man who has been accused by over a dozen women of various degrees of sexual abuse, and who has publicly bragged of his ability to assault women with impunity. With Moore adopting the Trump defense — all the women are liars, no matter how many there are and how much evidence there is in their favor — we should have known that sooner or later he'd rally to Moore's cause.

We also could have predicted it with a simple rule: Trump does what his base wants. If there's a conflict between his most rabid supporters and the Republican "establishment" — as there is in this case, since that establishment would like to be rid of Moore as quickly as possible (though they also want to do it in a way that allows them to hold on to the seat) — Trump will always side with the base. You can call that a political strategy, but it's also because he almost always shares their views.

And despite his repeated claim during the campaign that "with the exception of the late, great Abraham Lincoln, I can be more presidential than any president that's ever held this office," he has made no effort to be "presidential," despite the constant efforts of his staff to keep his impulses in check. Being the most powerful person on Earth has neither sated his bottomless need for adulation and praise, nor improved his ability to deal with attacks, nor made him less prone to lash out at those who criticize him.

Nor has it alleviated his malignant narcissism, as we can see in just a couple of recent examples. When he was asked about the large number of unfilled positions at the State Department, he responded, "I'm the only one that matters." When LaVar Ball, the father of a UCLA basketball player who had been accused of shoplifting on a trip to China, failed to thank Trump profusely enough for settling the matter, Trump tweeted, "It wasn't the White House, it wasn't the State Department, it wasn't father LaVar's so-called people on the ground in China that got his son out of a long term prison sentence - IT WAS ME." You'd think that becoming the president of the United States might have convinced him that he doesn't have to keep telling people he's a big shot, but you'd be wrong.

Every president will tell you that the unique challenges of the job altered them in some ways — made them more sober, or more humble, or more thoughtful, or taught them things they didn't know. Trump has so far been, and will almost certainly continue to be, the exception. He does not learn, he does not grow, he does not change.

So in any situation over the next three years, it won't be hard to predict how he'll act and what he'll decide. You only need ask some simple questions. What does Trump's base want? Then that's what he'll probably do. Is his ego being threatened? Then he'll lash out. Can he take credit for the work of others and blame others for his mistakes? Then that's what he'll do. Is there an opportunity to take the high road, or to eschew pettiness, or to delay the gratification of his id for the sake of a larger goal, or to reach out to those who don't already love him? Then he will let that opportunity pass.

Donald Trump is who he is, and he will never be anything else. You can count on it.