WASHINGTON — What happened to the evangelicals? They were supposed to be the bedrock of the Ted Cruz candidacy. Yet on Super Tuesday he lost them to Donald Trump.

Cruz still did make a reasonably good showing, winning Alaska, Oklahoma and Texas, the latter by an impressive 17 points. But he didn’t have the great night he needed to put away Marco Rubio and emerge as Trump’s one remaining challenger.

Cruz had done all the groundwork to win evangelicals and sweep the South by putting together strong alliances with local pastors and leaders. And yet, outside Oklahoma and Texas, he lost them to Trump by stunning margins — by 21 points in Alabama, 13 in Georgia, 14 in Tennessee, 16 in Virginia and 36 in, of all places, Massachusetts.

How could this have happened? A more scripturally, spiritually flawed man than Trump would be hard to find. As several anti-Trump evangelical voices have argued, Christian witness cannot possibly support a thrice-married man with such an impressive list of sins.

These theological arguments are both eloquent and impassioned but, in this season of fear and anxiety, beside the point. This time around, evangelicals are not looking for someone like them. They’re looking for someone who will protect them.

They’ve tried backing exemplary Scripture-quoting Christians — without result. After Mike Huckabee and Rick Santorum and considerations of Cruz himself, they are increasingly reluctant to support like-minded candidates who are nonetheless incapable of advancing their cause in a hostile political arena so dominated by secularism.

They have no illusions about Trump. They have no expectations of religious uplift. What he offers them is not spirit but “muscle.”

The transaction was illuminated by Trump’s January speech at Liberty University. His earlier halfhearted attempts to pose as a fellow evangelical were amusing and entirely unconvincing. At Liberty, he made another such I’m-one-of-you gesture by citing a biblical verse, betraying a risible lack of familiarity with biblical language and usage.

Yet elsewhere in the speech, he described how Christians abroad are being massacred and Christians here at home are under cultural and political siege. He pledged: “We’re going to protect Christianity.”

Not just Christians, but Christianity itself. What Trump promises is to stand outside the churchyard gates and protect the faithful inside. He’s the Roman centurion standing between them and both barbarians abroad and aggressive secularists at home.

The message is clear: I may not be one of you. I can’t recite or even correctly cite Scripture. But I will patrol the borders of Christendom on your behalf.

Evangelicals answered resoundingly. They went for Trump in a rout.

The essence of Trump’s appeal everywhere, far beyond evangelicals, is precisely the same: “I’m tough, I will protect you.” That’s why he remains so bulletproof. His lack of policy, the contradictory nature of his pronouncements that pass as policy — especially their capricious eruption and summary abandonment — have turned out to be an irrelevance.

Who cares? His support has nothing to do with actual prescriptions. Tuesday night, the immigration issue ranked low among Republican voters’ concerns. Only about 10 percent deemed it their No. 1 issue. The political success of Trump’s draconian immigration stance lies not in the policy but in the attitude — a not-going-to-take-it-anymore defiance.

That’s the reason none of the rhetorical outrages that would have destroyed another candidacy have even left a mark on Trump. He mocks John McCain’s heroism, insults Carly Fiorina’s looks, fawns over Vladimir Putin — nothing. If anything, he gains support for fearless “telling it like it is” candor.

This is a man who three times last Sunday refused to disavow David Duke and the Ku Klux Klan. No other candidate could survive that. Trump not only survives, he thrives.

Which is why the only possible way to stop Trump is a full-scale, open-the-bomb-bay-doors attack on the very core of his appeal: his persona of the tough guy you can trust to protect you.

It may be too late. But everything else will simply bounce off the Teflon.

Charles Krauthammer is a columnist with the Washington Post Writers Group.