If you watched tonight’s GOP debate and are still confident in your decision to support Donald Trump, then you and I live on the same planet, but in different worlds. Tonight was a disaster for Trump. There can no longer be any doubt of these things:

1. That he is a thoroughly untrustworthy character. The Trump University debacle was devastating to him tonight. He had no plausible answers at all for the damning facts against him, just bluster and name-calling. Rubio and Cruz were merciless against Trump on his hypocrisy on foreign workers and American jobs. Plus, he looked comically evasive on the question of the New York Times off-the-record transcript. He plainly told the Times editorial board off the record that he doesn’t mean what he says on immigration. If you believe otherwise after tonight, you will believe anything.

2. That he will say anything to get elected. I am not sure if this is intentional. I think he says anything that comes to mind.

3. That he comes across as temperamentally unsuited to hold the presidency. He can’t take criticism, and can’t answer his critics with anything but the heat of a flaming gasbag. How can we trust someone so unstable with the power to start a war? When Rubio rattled him, he called him “Little Marco” — a remark that did not make Rubio look small, but rather Trump.

None of this is new, of course. But all of it came through with such force in tonight’s debate that it was finally impossible to give Trump the benefit of the doubt. He fell apart under attack.

The decisive moment for me, though, was when Trump insisted — and later repeated — that if he gave an illegal order to the US military, that they would follow it. He was proud of this! This is a man who cannot be counted on to respect the rule of law, and would even be willing to cause a constitutional crisis over it.

As regular readers know, I have a lot of sympathy for people who like Trump, and I have been grateful to Trump for some of the things he has done in this campaign (most especially for breaking the ridiculous GOP taboo on criticizing the Iraq War). I do not pity the Republican Party its travails over Trump, because it deserves to be cold-cocked over its misrule. Here’s the thing, though: there are millions of people who believe in Donald Trump, and who believe that he will do the things he says. Many of them have been let down by life. They’re scared of the future, and they have reason to be. They don’t believe that the Republican Party has their back, and they’re probably right about that.

What happens if Donald Trump is elected president, and can’t deliver on his gaudy promises? There’s no way he’s going to be able to do the things he says. Being president of the United States is not like running your own company. Trump doesn’t even know his own mind. Every time he got in trouble in tonight’s debate (which was a lot), he quickly retreated to Trumpenprinzip: the obnoxious assertion that Trump is the best leader because he’s got the best polling numbers. He’s a man who believes that the truth is what he says it is. If he becomes the next president, and if — no, when — he betrays all the people who voted for him believing he was a man of his word, a man who would be for them, things are going to get very ugly, very fast in this country.

What a ridiculous spectacle the Republican Party has become. Watching tonight’s debate in front of a hooting mob of goons was to witness genuine decadence. Read John Cassidy’s New Yorker piece — written before tonight’s debate — about why he thinks the GOP establishment’s #NeverTrump efforts are going to fail. Excerpts:

In rallying disaffected Republicans and independents, he has identified a set of internal contradictions in the G.O.P. that no amount of negative advertising can conceal. And rolling out somebody like Romney only highlights these contradictions.

For decades now the Republican Party has been appealing to low-income and middle-income whites while promoting an economic agenda that runs contrary to their interests: tax cuts for the rich, deregulation, free trade, deep cuts to entitlement programs, and so on. Trump, who is hawking a tax plan that he appears to have ordered up at short notice from Art Laffer or Larry Kudlow, can be accused of adopting the same bait-and-switch tactics, but taxes aren’t central to his campaign. In promising to end illegal immigration and impose hefty tariffs on good from countries like China and Mexico, he can, at least, claim to be pursuing an agenda that would boost American wages and save American jobs.

Would his strategy work? Probably not. But in talking about safeguarding Social Security, forcing pharmaceutical companies to lower their prices, preventing people who don’t have health insurance from dying in the streets, and eliminating tax breaks that favor hedge-fund and private-equity managers (such as Romney), Trump is using the language of economic populism in a manner that none of his Republican rivals can match. Beholden to their campaigns backers, they are forced to confine themselves to the standard guff about cutting taxes, loosening regulations, and encouraging enterprise. At this late stage, many none-too-affluent G.O.P. voters appear to be smelling a rat.

He goes on to quote reformist Republican Reihan Salam’s recent piece saying that the GOP really hasn’t done jack for working-class people, and that it needs to make substantive policy changes to “reinvent itself as the champion of America’s working- and middle-class families.” Cassidy is skeptical that Republican politicians can do that because it would require them to go against the interests of their deep-pocketed donors.

And there’s this:

As New York magazine’s Jonathan Chait commented on Twitter on Thursday, “#NeverTrump, at its core, is people satisfied that the Republican Party is fundamentally sound.” And that, in the final analysis, is why they are unlikely to be able to see off Trump’s insurgency.

Read the whole thing. If you watched that bizarre spectacle in Detroit tonight and believed that the Republican Party is in any way sound, you should consider that Trump voters aren’t the only Republicans prone to magical thinking. Consider: after doing an effective job showing that Trump is a reckless mountebank who would threaten American democracy, Cruz and Rubio agreed at debate’s end that they would support him if he’s the nominee — thereby massively undermining their argument.

Trump, with his remarks on being willing to deliver illegal orders to the US military, and expecting them to obey, revealed himself to be a man in search of a balcony. They would campaign for Donald Duce? Really? That being the case, how bad do they really think Trump is? Or does party matter more than principle? It’s crazy — just think of how much good either Rubio or Cruz could have done for their candidacies by refusing to support nominee Trump. They’re trying to convince Republican voters that Trump is a mortal threat to the GOP and to America itself … but in the end, they’ll fall in line behind him, if he gets the nomination.

That’s leadership?

UPDATE: Matt Yglesias makes a good point:

But for all their attacks, they are not really joining the argument that Trump started over the proposition that the GOP should ditch elements of free market ideology and embrace populist nationalism instead.

Trump’s rivals don’t want to engage in this argument for the same reason that Trump has rocketed to the polls — most rank-and-file Republicans agree with Trump. So instead, they bite at him over secondary issues — old campaign contributions to Hillary Clinton, Trump University — or try to point out problems with Trump that also apply to the other candidates. It was shocking, for example, to see Fox News anchors pointing out that Trump’s tax plan isn’t remotely paid for. This is entirely true, but it’s equally true of every other GOP tax plan of the past 15 years and it never seemed to bother Fox before.

These are real knocks on Trump but they don’t explain the GOP establishment’s rage against him. That stems from the divide over the role of populist nationalism in the conservative movement. And whether the establishment candidates want to talk about it or not, the delegate math has now reached a point where a major intra-party blowup is essentially inevitable.