Ted Cruz, right, and Donald Trump at the Republican presidential debate in Detroit last month. (Jim Young/Reuters)

Yes, the big Wisconsin story is Ted Cruz’s crushing 13-point victory. And yes, it greatly improves his chances of denying Donald Trump a first-ballot convention victory, which may turn out to be Trump’s only path to the nomination.

Nonetheless, the most stunning result of Wisconsin is the solidity of Trump’s core constituency. Fundamentalist Trumpism remains resistant to every cosmic disturbance. He managed to get a full 35 percent in a state in which:

● He was opposed by a very popular GOP governor (80 percent approval among Republicans) with a powerful state organization honed by winning three campaigns within four years (two gubernatorial, one recall).

● He was opposed by popular, local, well-informed radio talk show hosts whose tough interviews left him in shambles.

● Tons of money was dumped into negative ads not just from the Cruz campaign and the pro-Cruz super PACs but from two anti-Trump super PACs as well.

Republican front-runner Donald Trump says he can't wait to take on Democratic front-runner Hillary Clinton in the fall, but here are three reasons why he could lose a general election. (Sarah Parnass/The Washington Post)

And if that doesn’t leave a candidate flattened, consider that Trump was coming off two weeks of grievous self-inflicted wounds — and still got more than a third of the vote. Which definitively vindicated Trump’s boast that if he ever went out in the middle of Fifth Avenue and shot someone (most likely because his Twitter went down — he’d be apprehended in his pajamas), he wouldn’t lose any voters.

The question for Trump has always been how far he could reach beyond his solid core. His problem is that those who reject him are equally immovable. In Wisconsin, 58 percent of Republican voters said that the prospect of a Trump presidency left them concerned or even scared.

Cruz scares a lot of people, too. But his fear number was 21 points lower. Moreover, 36 percent of Wisconsin Republicans, facing a general-election choice between Hillary Clinton and Trump, would either vote Clinton, go third party or stay home.

Trump did not exactly advance his needed outreach with his reaction to the Wisconsin result: a nuclear strike on “Lyin’ Ted,” as “a puppet” and “a Trojan horse” illegally coordinating with his super PACs (evidence?) “who totally control him.” Not quite the kind of thing that gets you from 35 percent to 50 percent.

Not needed, say the Trumpites. If we come to Cleveland with a mere plurality of delegates, fairness demands that our man be nominated.

This is nonsense. If you cannot command or cobble together a majority, you haven’t earned the party leadership.

John Kasich makes the opposite case. He’s hanging on in case a deadlocked convention eventually turns to him, possessor of the best polling numbers against Clinton. After all, didn’t Lincoln come to the 1860 convention trailing?

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Yes, and so what? The post-1968 reforms abolished the system whereby governors, bosses and other party poo-bahs decided things. In the modern era, to reach down to the No. 3 candidate — a distant third who loses 55 of 56 contests — or to parachute in a party unicorn who never entered the race in the first place would be a radical affront to the democratic spirit of the contemporary nominating process.

A parachute maneuver might be legal, but it would be perceived as illegitimate and, coming amid the most intense anti-establishment sentiment in memory, imprudent to the point of suicide.

Yet even without this eventuality, party suicide is a very real possibility. The nominee will be either Trump or Cruz. How do they reconcile in the end?

It’s no longer business; it’s personal. Cruz has essentially declared that he couldn’t support someone who did what Trump did to Heidi Cruz. He might try to patch relations with some Trump supporters — is Chris Christie’s soul still for sale? — but how many could he peel away? Remember: Wisconsin has just demonstrated Trump’s unbreakable core.

And if Trump loses out, a split is guaranteed. In Trump’s mind, he is a winner. Always. If he loses, it can only be because he was cheated. He constantly contends that he’s being treated unfairly. He is certain to declare any convention process that leaves him without the nomination irredeemably unfair. No need to go third party. A simple walkout with perhaps a thousand followers behind will doom the party in November.

In a country where only 25 percent feel we’re on the right track and where the leading Democrat cannot shake the challenge of a once-obscure dairy-state socialist, you’d think the Republicans cannot lose.

You’d be underestimating how hard they are trying.

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