Not surprisingly, though, Trump isn’t very good when he has to defend any position at length from any kind of determined critique. And he hasn’t really had to do that, across multiple Republican debates, because he’s been sharing a stage with five or six or seven other candidates, and because those other candidates have mostly avoid tangling with him, on the misguided theory that he would ultimately beat himself. Indeed, he still didn’t have to defend himself that much last night, because whenever he and Rubio really got into it the bell dinged and it was time to have John Kasich or Ben Carson ramble for a while. The debate would have been a lot worse for him if he had been on stage with Rubio and Cruz, and only them; instead, the format repeatedly bailed him out.

Which it won’t come the fall, when should he win through, he will be on the stage with Hillary and only Hillary — barring a third party run of course. Clinton is not a charismatic politician or a particularly effective public speaker, but she is a pretty good debater, she knows policy as well as anyone in politics, she’s tangled very effectively with Republican men on various platforms (ask Rick Lazio or the Benghazi Committee), and there’s no way she’s going to let Trump get away with the “five slogans, insult, mic drop” approach to debating that’s carried him thus far. So he will need to evolve, and radically, as a debate-stage performer — which I suppose is always possible — or else he’ll simply get embarrassed, at length, in the highest-profile moments of the campaign.