When she isn’t dispensing makeup tips on Instagram, Rep. Alexandria Ocasio-Cortez dispenses sophomoric political maxims, most recently in her defense of “purity tests.”

The stink of impurity here is upon Pete Buttigieg of Harvard and McKinsey, who had a fundraiser with some well-off people who drank a few $900 bottles of wine with some Napa vintners who are longtime Democratic donors. One of Mayor Pete’s primary rivals, Sen. Elizabeth Warren, made a fuss about that fundraiser at the last debate. (Never mind that she is no stranger to big-money events herself.) Buttigieg dismissed the criticism as a silly “purity test,” but Ocasio-Cortez, speaking at a rally with another Democratic primary candidate — her fellow socialist, Sen. Bernie Sanders — took a stand for shallow fanaticism.

“For anyone who accuses us for instituting purity tests,” she said, “it’s called having values. It’s called giving a damn. It’s called having standards for your conduct to not be funded by billionaires but to be funded by the people.”

Oh, the people.

You’d think that a former New York bartender wouldn’t need it explained to her, but you don’t have to be John Kerry, enthusiastic collector of heiresses (the current Mrs. K. is worth about $1 billion), to buy a $900 bottle of wine — or to sell one, something that is of interest to the farmers and merchants who earn a living from the nation’s thriving grape trade. They’re “the people,” too.

But “billionaires” are the bogeymen of the moment, not only for Ocasio-Cortez and Sanders but also for Sen. Warren, who hates plutocrats so much that at Harvard she occupied a chair endowed by Cleary Gottlieb, a law firm that helped big banks that did business with Bernie Madoff avoid compensating his victims.

Ocasio-Cortez’s complaint is inescapably dopey. There are right-wing billionaires such as Rebekah Mercer, left-wing billionaires such as George Soros, libertarian billionaires such as Charles Koch, soda-obsessed billionaires such as Michael Bloomberg — billionaires come in all political flavors.

Meanwhile, Warren and Joe Biden are rich, and Bernie Sanders has quite the portfolio of dachas. That tells us donkey squat about the value of what those politicians believe. In principle, a good political platform is a good political platform whether it comes from a candidate whose average donation is eleven bucks or eleven hundred bucks.

But Ocasio-Cortez’s beef here is not what Pete Buttigieg believes about taxes, national defense or health care. It is about the heroic self-conception of the Left, the self-appointed tribunes of the plebs — not that they ever asked the plebs, who don’t seem to care much one way or the other how Mayor Pete gets his green.

In fact, the plebs are not exactly a political monolith, either: Sen. Sanders raises his money mainly from small donations, but so does Donald Trump, who saw an average donation of $48 from 725,000 donors in his big summer fundraising push.

If anything, the electoral success of Donald Trump, who satisfies no sensible person’s notion of political purity, suggests that “the people” often take a more realistic approach to their politicians.

Ironically, it is conservative Christians who have developed the most pragmatic view. While some Evangelical intellectuals have been anguished (with good reason) about their community’s passion for Trump, the rank and file have been more than happy (probably too much more than happy) to accept their judges and their modest political victories from the unclean hands of Trump. It would be better if he were better, their argument goes, but they’ll take what they can get.

They are not necessarily wrong. If politics is going to be about policy, then politicians are only tools. But when politics is a contest of tribal totems, then policy has to take a second place to all sorts of cultural signifiers. And that is the kind of politics Ocasio-Cortez practices: Us and Them, white hats and black hats, Hatfields and McCoys, etc. Nowhere is this tendency stronger than in presidential campaigns.

Some voters are very into that sort of thing. You’ll find the purity police on social media. They are hysterical and callow, like Ocasio-Cortez herself. Other voters only want sensible policies, effective government and reasonable taxes. They are less interested in seeing Pete Buttigieg canceled for the crime of assaulting a 98-point cabernet than they are in whether his health-care plan is any good.

(It isn’t, but that’s not the point.)

Kevin D. Williamson is the author of “The Smallest Minority: Independent Thinking in the Age of Mob Politics,” out now.