The reigning idiocy of the current political season is the incessant tossing around of “establishment,” an epithet now descending into meaninglessness. Its most recent abuse is by Donald Trump supporters rationalizing his Iowa defeat with the following consolation: If you tally up Trump and Ted Cruz (and throw in Ben Carson), a whopping 60 percent of the vote is anti-establishment!

So what? The threat to the GOP posed by the Trump insurgency is not that he’s anti-establishment. It’s that he’s not conservative. Trump winning the nomination would convulse the Republican Party, fracture the conservative movement and undermine the GOP’s identity and role as the country’s conservative party.

There’s nothing wrong with challenging the so-called establishment. Parties, like other institutions, can grow fat and soft and corrupt. If by establishment you mean the careerists, the lobbyists and the sold-out cynics, a good poke, even a major purge, is well-deserved.

That’s not the problem with Trump. The problem is his, shall we say, eclectic populism. Cruz may be anti-establishment but he’s a principled conservative, while Trump has no coherent political philosophy, no core beliefs, at all. Trump offers barstool eruptions and whatever contradictory “idea” pops into his head at the time, such as “humane” mass deportation, followed by mass amnesty when the immigrants are returned to the United States.

That’s the reason his harebrained ideas — barring all Muslims from entering the country, a 45 percent tariff on Chinese goods, government-provided universal health care through “a deal with existing hospitals to take care of people” (why didn’t I think of that?) — have received such relatively little scrutiny. No one takes them seriously. His actual platform is all persona — the wonders that will emanate from his own self-proclaimed strength, toughness, brilliance, money, his very yugeness.

Trump’s is faith-based politics of the Latin American caudillo variety. “At the [Sarah] Palin rally,” reports John McCormack of The Weekly Standard, “Trump promised he would localize education. ‘How?’ shouted one man in the crowd. ‘Just you watch,’ Trump replied.” Meaning: I have no idea. Just trust me.

Cruz does not lack for self-confidence. And he constantly wraps himself in anti-establishment rhetoric. He reasonably calculates that his hard-edged conservatism sells best when presented not as pristine ideology but as a revolt against entrenched interests.

To imagine, however, that his railing against “the Washington cartel” makes him a Trumpian brother-in-arms is to mistake tactics for strategy, style for substance. To be sure, it’s a misperception Cruz himself encouraged throughout 2015 as he drafted in Trump’s wake. But that’s yesterday’s story. It’s been over for weeks.

The story since January is of a bromance blown up, clearing away the anti-establishment veneer and allowing their fundamental political differences to finally emerge:

—Over Trump’s “New York [read: liberal] values.”

—Over government power. Cruz’s most biting commercial showed Trump enlisting government to tear down the home of a little old lady standing in the way of a casino parking lot.

—Over ethanol, which Cruz opposed on classic small-government grounds that the state should not be picking winners and losers, and which Trump supported because “it happens to be a lot of jobs for Iowa.”

The Iowa results clarified the dynamic of the Republican race. There are only three candidates in the race and, as I argued last week, each represents a different politics. The result is a three-way fight between Trump’s personalized strongman populism and two flavors of conservatism — Marco Rubio’s more mainstream version and Cruz’s more uncompromising take-no-prisoners version.

We can now read the Iowa results as they affect the Republican future. Trumpian populism got 24 percent, conservatism (Rubio plus Cruz) got 51 percent. There will be a spirited contest between the two conservatives over who has the better chance of winning the general election and of governing effectively. But whatever the piques and preferences of various “establishment” party leaders, there’s no denying that either Rubio or Cruz would retain the GOP’s fundamental ideological identity. Trump would not.

Getting thumped in Iowa does not mean that Trump is done. He’s on favorable ground in New Hampshire and leads in practically every other state. But he’s in for a long fight.

What Iowa confirms is that whatever beating the “establishment” takes during this campaign, Republicans are choosing conservatism over Trumpian populism by 2 to 1. Which means their chances of survival as the party of Reagan are very good.

© 2016, The Washington Post Writers Group