This is almost always true:

A woman who aborts a child is operating within an emotional and spiritual context of fear, disappointment, confusion and sadness. If she receives an illegal abortion she should not be “punished” by the law. This is in line with long human tradition and is based on the simple wisdom that she has already been gravely and tragically penalized: She has lost her child, someone who was very likely going to love her, someone she very likely would have loved. The doctor who performs such an abortion on the other hand is not in turmoil, he is in business. He breaks the law and ends the life of the child with full consciousness, and for profit. He should be “punished.” He should be in jail.

That we even have to discuss this is absurd. It also feels very 1970s, when the subject to so many was new. I guess it’s still new to Donald Trump, and so unexamined, un-thought-through. Yes, he walked back or clarified his stand on punishment, and yes, Chris Matthews badgered and browbeat him on MSNBC. But presidential hopefuls, especially Republican ones, are routinely badgered and browbeaten. You have to deal with it. It’s part of how you earn the big job.

But I feel like we’re missing something in this latest.

Mr. Trump is hurting himself, in real time and for the first time. We will likely see it, and soon, in the polls. Already his numbers in next week’s Wisconsin primary have fallen, and as for women—well, with women nationally Mr. Trump is currently more popular than cholera, but not by much.

We’re missing what’s happening because we’re blocked by clichés. The first great Trump cliché, which began seven or eight months ago, was that he’d quickly do himself in with some outrageous comment. So everyone waited. His insults to John McCain, Megyn Kelly—that would do it. But it didn’t. The more outrageous he was the stronger he got.

So a new cliché was born, the still-reigning one: Whatever Mr. Trump says it won’t hurt him, people will just love him more.

But that’s not right. It was always a mistake to think one explosive statement would blow his candidacy up. What could damage him, and is damaging him, is the aggregate—a growing pile of statements and attitudes that becomes a mood, a warning sign, a barrier.

It’s been going on for four or five weeks, and you can take your pick as to the tipping point. Maybe it was when he threatened to “spill the beans” on another candidate’s wife, or when he retweeted the jeering pictures of her and his own wife. Maybe it was his inability to clearly, promptly denounce the KKK; maybe it was when he hinted at riots if he’s cheated out of the nomination. Maybe it was Corey Lewandowski’s alleged battery of reporter Michelle Fields. Maybe it was when Mr. Trump referred in debate to his genitals, a true national first.

It has all added up into a large blob of sheer dumb grossness. He is now seriously misjudging the room. The room is still America.

I speak to Trump supporters a lot, and they are getting embarrassed. Their feeling was perfectly encapsulated by what Ann Coulter said on a podcast after the retweeting of the wives’ photos: “Do you realize our candidate is mental?” She said of having to defend his mad statements and tweets: “It’s like constantly having to bail out your 16-year-old son from prison.”

It has left me thinking about the political theory of The Mess. The Mess is something a candidate occasionally brings with him that voters can tell is going to cause trouble down the road. The Mess is a warning sign; it tells potential supporters to slow down, think twice. The Mess might be a pattern of scrapes with the law, a series of love affairs or other scandals. Voters will accept normal, flawed human beings but they don’t like patterns of bad behavior. They don’t like when they see a Mess, because they don’t want to elect trouble to high office. Donald Trump’s Mess is his mouth, his indiscipline, his refusal to be . . . serious.

At the same time Mr. Trump doesn’t even seem to be trying to do the one big thing he has to do now. He is the front-runner for the nomination. At this point it is his job to keep the support he has and persuade those who don’t like him to give him a second or third look. To do that he only has to be more thoughtful, stable and mature in his approach—show he may be irrepressible and fun and surprising, even shocking, but at bottom he has within him a plausible president.

Instead, he is stuck at nutty. Rather than attempt to win over, he doubles down. In the process he shows that what occupies his mind isn’t big issues, significant questions or the position of the little guy, but subjects that are small, petty, unworthy.

Instead of reassuring potential or reluctant supporters, he has given them pause. Instead of gathering in, he is repelling. This is political malpractice on a grand scale.

It was always Mr. Trump who was the only one big enough to take down Mr. Trump. He may be doing it. In the process he does a great favor to his current and potential opponents. One of the things Mr. Trump does is make everyone else look normal. His outrageousness cancels out theirs. Once Hillary Clinton was too corrupt to be elected, had too many negatives, too much bad history from her early days in Arkansas to the Clinton Foundation, Benghazi, the emails. She brought and brings quite a mess.

But his mess cancels out her mess.

The sheer force of Donald Trump’s weird, outsized strangeness has made her look normal. It’s made Ted Cruz look normal too, like a nice, sincere fella right in the middle of the political bell curve.

There are people who used to dismiss Trump supporters, and who later self-corrected to show compassion from great heights: “My God, they’re suffering in America.” They have now taken a newly jaundiced eye—his supporters are his enablers.

My thought is different. Maybe the sadness here is that Mr. Trump’s supporters are earnest and full of concern for America and he isn’t worthy of them. Maybe he only harnessed their legitimate anger but can’t do anything with it because he’s not as serious as so many of them are, but a flake, a dope with poor impulse control.

What happens to Trumpism—his stands on illegal immigration, trade, entitlements—when Mr. Trump is gone? Does he have any sense of responsibility for what he leads?

And the immediate question: Is it possible he can change and be worthy of the moment? I don’t know but doubt it, because in my observation people at the end of middle age don’t usually change, they just become more so. In any case it’s getting late. So far Donald Trump has conquered all expectations, half-conquered the American political system, and almost conquered one of our two great political parties. It is sad he can’t conquer himself.