The day after his address at the close of the RNC, Trump decided to tear into Ted Cruz and to repeat some of his most scurrilous and over-the-top accusations (some couched in the form of “questions”) against Cruz and his family. In addition, there’s a report (perhaps true, perhaps not) that Trump has vowed to spend tons of his own money on a super PAC to destroy the careers of both Cruz and Kasich. Even if the latter threat is one he actually made, I would bet he’s not going to actually do it. But it’s the typical Trumpian threat (remember when he said he would go to court to find out if Cruz was a natural-born citizen, for example?).

So, why would Trump be dissing Cruz (and perhaps Kasich) the day after his triumphant acceptance of the GOP nomination? It wouldn’t be because they’re too conservative or too liberal—Kasich was the most liberal of all the people running against Trump, Cruz probably the most conservative. It wouldn’t be because they haven’t endorsed him; several others haven’t endorsed him, either (although they don’t hold office: Fiorina and Jeb Bush come to mind). It wouldn’t be because they did or didn’t come to the convention; Cruz did and Kasich didn’t.

It may be in part because they were both the last men standing towards the primary season’s end. It’s also clear that Cruz is Trump’s main target rather than Kasich, probably because Cruz is the strongest and most potentially powerful of Trump’s primary rivals who wouldn’t kiss his butt in the end (sorry for the crassness of the language, but with Trump it’s apropos).

Trump hates anyone who doesn’t ultimately kiss his butt, and that makes him want to make them kiss his butt or at least to humiliate them greatly. This is not some new behavior of Trump’s since he’s become a candidate; it’s a trait he’s had for decades: he is tremendously vindictive, as you can discover from his Twitter history, his litigation history, and any biography of the man.

Trump tried to humiliate and even destroy every single one of his major opponents in turn during campaign 2016. But not one of them has he tried to slander as much or for as long a time as he’s attacked Cruz (of course, some have now joined his campaign, such as Carson). For the most part, he attacked them until they fell in the polls, and then he moved on to the next contender.

But Cruz’s head is bloody but unbowed. It’s not enough for Trump to have defeated him, he is out to destroy him politically and personally for the future, too, if he can accomplish that. Call Trump an “alpha male” if you wish, but real alpha men don’t need to do this, although narcissistic bullies do (I wrote previously on the subject of whether Trump is an alpha male here). And I don’t care how many times Trump’s kids say what a nice guy he is. He may be nice to them, and he may be nice to those who show him the proper obeisance, but to anyone who crosses him he is not only out to criticize but to humiliate and destroy them, if possible.

Now, many politicians are vindictive or fond of showing subordinates that they’re the boss. LBJ was famously the latter, for example (as well as coarse), sometimes liking to receive people while sitting on the toilet in order to demonstrate his dominance over them. But he did this to aides rather than enemies, it certainly wasn’t done in public, and it didn’t involve vicious slurs on their wives or fathers. Here’s the way it went:

LBJ was well-known (although the stories only came out publicly some time after his presidency was over) for insisting that aides accompany him to the toilet, where he continued to talk to them. It was a sort of test: Johnson also upset aides with his habit of adjourning a conversation to the bathroom when the need arose. Those who were reluctant to follow him to the toilet were a source of great amusement to him. He frequently recounted a story about “one of the delicate Kennedyites who came into the bathroom with me and then found it utterly impossible to look at me while I sat there on the toilet. You’d think he had never seen those parts of the body before. For there he was, standing as far away from me as he possibly could, keeping his back toward me the whole time, trying to carry on a conversation. I could barely hear a word he said. I kept straining my ears and then finally I asked him to come a little closer to me. Then began the most ludicrous scene I had ever witnessed. Instead of simply turning around and walking over to me, he kept his face away from me and walked backward, one rickety step at a time. For a moment there I thought he was going to run right into me. It certainly made me wonder how that man had made it so far in the world.”

Trump doesn’t invite aides into the toilet, as far as I can see. What he does instead is public and libelous. It seems he cannot resist grinding into the dirt those people he thinks have consistently opposed him, and he doesn’t care how dirty he becomes in the process. Yes, “he fights,” and that’s something the GOP has needed for a long, long time. But there are ways to fight and targets to choose, and this just makes him look bad, petty, and even crazy—solidifying the perception (right or wrong) among many people that he’s a loose cannon with poor impulse control. That’s not what’s wanted in a president.

Cruz is gambling that taking the high road and also keeping away from an endorsement of Trump will hold him in good stead, four years from now.

[NOTE: See also this.]