My preview of the debate yesterday focused on the fact that Trump’s “serious” debates at the end of the primaries, when there were fewer rivals, gave us some clues about how he might perform in the main event. He was aggressively incoherent and sometimes completely unintelligible, proving repeatedly that he had absolutely no idea what he was talking about.

This has been obvious from the beginning of his campaign if you watched his rallies and interviews. It’s just that his personality is so remarkably bizarre that I think the lack of substance is easy to overlook. (I confess I have been somewhat surprised that so many people find his rambling “braggadociousness” appealing enough that they fail to notice that he is ignorant about everything important to the job of president.)

In recent days with the hiring of campaign manager Kellyanne Conway and CEO Steve Bannon as well as sage advice from his pal Roger Ailes, Trump has been tamed just enough to read a stump speech on a teleprompter, and he’s sounded a bit more intelligible.

So there was always the possibility that he would have done a little bit of prep work, read a briefing paper or two and otherwise taken the debate seriously. It is the most important office in the world, after all. It wouldn’t hurt to do a little cramming on the details before appearing in front of 100 million people to make the case for why you are the best person for the job.

Trump’s campaign made it very clear that he wasn’t doing any of that, but I think many political professionals assumed there was a large element of spin involved. He had to have at least done some practice debates, right? But it turns out that for the first time his campaign was telling the whole truth.

Last night Donald Trump demonstrated not only that he didn’t prepare but that he has no underlying knowledge of the subjects a president is required to know. He simply tried to bluff his way through with incoherent misdirection, hostility and sarcasm, even as he made the absurd claim that his temperament is his best quality. He gave the worst debate performance of his short political career. In fact, it may have been the worst debate performance of any political career.

I wasn’t sure whether or not Hillary Clinton would be able to handle him. It’s disorienting to see someone spout gibberish at such an important event, particularly when it’s combined with Trump’s narcissism, as when he oddly asserted that Clinton only started talking about jobs in response to his candidacy, or that NATO created a terrorism policy because he goaded them into it. (That’s ludicrous, of course.) But she handled him well, with humor and authority, proving that it can be done.

The reviews all seemed to indicate that Trump’s best moments were his early comments on trade policy. Which is probably true but it’s not saying much. He name-checked some Rust Belt states where the issue is particularly salient, which shows that he may have had some coaching. But his obsession with the subject, to the exclusion of all other economic concerns, is one-dimensional to say the least.