NEVER GET BETWEEN WEALTHY OLD WHITE PEOPLE AND THEIR GOVERNMENT BENEFITS:

[T]he libertarian moment was momentary indeed. The Republican presidential primary was upended not by Rand Paul but by Donald Trump, whose agenda is the exact opposite of libertarianism in almost every way. Libertarians want open borders; Trump promises to build a wall with Mexico and deport millions of illegal immigrants. Libertarians want to privatize Social Security; Trump has defended Social Security and Medicare. Libertarians want to cut defense spending; Trump wants a big military, though he promises not to use it unwisely. And, among Republicans, Trump is a relative dove. The others in the GOP field compete to be more bellicose than Barack Obama or Hillary Clinton.

Paul, meanwhile, has all but disappeared from view. Humiliated in the first Republican debate, when he challenged Trump to promise not to run an independent campaign, Paul alienated many of his noninterventionist fans and looked like just another politician instead of a principled libertarian when he came out against the Iran deal. His newfound hawkishness has not helped him. His poll numbers among Republican candidates have collapsed from 10 percent last April to between 2 percent and 3 percent now. It remains to be seen whether his polling numbers will be high enough to let him be onstage at the next Republican debate. On October 15, Paul's campaign staff released a memo declaring that he is not dropping out of the race, never a good sign.

Whether Paul stays in the race or not, the libertarian moment he symbolized is over. To be more precise, it never existed.

Libertarians, like neoconservatives, are overrepresented among op-ed writers and TV talking heads and think-tank wonks on the right. But neither the Club for Growth wing nor what conservative writers Reihan Salam and Ross Douthat call the Sam's Club wing of the GOP is libertarian, except when it suits them.

Unlike ideological libertarians who fantasize about the replacement of fiat money with gold or bitcoin, most Wall Street Republicans object to regulations they dislike, such as Dodd-Frank, while remaining content with a system that gives capital-gains income preferential tax treatment and socializes the cost of bank bailouts while privatizing the benefits.

For their part, white working-class conservatives--nativist, protectionist and often religious--are to libertarians what matter is to antimatter. Over the years, Rand Paul's father, Ron Paul, managed to attract a variety of right-wing extremists who were not consistent libertarians, like gold bugs and racists. Since the Nixon era, the small number of actual Republican libertarians have been fleas hitching a ride on the dog of George Wallace-style populism--and in the Time of Trump, the fleas have fled the dog.

What holds together the donor class and populist wings of the GOP is not libertarian philosophy, but a policy: deficit spending. The Republican rich want lower taxes and lower spending. Many Republican populists want middle-class entitlements, if not spending on the poor, to be maintained. The only way to cut tax rates on rich Republicans while maintaining spending on the entitlements of middle-class Republicans is to run perpetual deficits. The fact that all of the economic plans of leading GOP presidential contenders, including Trump's plan, would blow holes in the federal budget by slashing rates on the rich without cutting middle-class benefits is not a mistake; it's a feature.

Follow @brothersjudd