The candidates carrying on this tradition in the Democratic primary are Pete Buttigieg, Elizabeth Warren and the late-entering Michael Bloomberg — Buttigieg and Bloomberg as center-left figures, Warren as the progressive promising to direct her “I’ve got a plan for that!” wonkery to more ambitious ends.

But Sanders is different; he has policy plans, too, but he’s fundamentally a moralist arguing for a politics of righteous struggle, in a way that separates him from Warren as well as from Buttigieg or Bloomberg. And just as Donald Trump benefited in 2016 — and figures like Ted Cruz and Jeb Bush suffered — from a sense that the G.O.P.’s libertarian and neoconservative intelligentsia bore some responsibility for the double disasters of Iraq and the financial crisis, Sanders benefits from a widespread left-wing disappointment with what the Obama-era politics of expertise produced.

This disappointment has been strongest on health care, where Obamacare’s most popular provision was the simple socialism of the Medicaid expansion rather than the complicated, expert-fashioned architecture of the exchanges. But it’s also palpable in education policy, where after two decades worth of technocratic experiments — Race to the Top, Common Core, etc. — we have chronically disappointing test scores, persistent racial gaps, the same basic stagnation despite reformers’ best-laid plans.

On both issues and others, the appeal of Sanders has less to do with the details of his plans and more to do with a simple formulation: The experts had their chance; let the moralists and radicals have theirs.

However, that’s only one possible response to disillusionment with technocracy. The other response is to prefer a return to transactional politics, to dealmakers who keep the system running rather than optimizing for efficiency, to machine politicians who aren’t going to dramatically improve the status quo but also aren’t likely to embrace clever plans that accidentally make it worse.