And I’m not just talking about the politicians; I’m talking about the wonks. It’s remarkable how many supposed experts on health care made claims about Obamacare that were clearly unsupportable. For example, remember “rate shock”? Last fall, when we got our first information about insurance premiums, conservative health care analysts raced to claim that consumers were facing a huge increase in their expenses. It was obvious, even at the time, that these claims were misleading; we now know that the great majority of Americans buying insurance through the new exchanges are getting coverage quite cheaply.

Or remember claims that young people wouldn’t sign up, so that Obamacare would experience a “death spiral” of surging costs and shrinking enrollment? It’s not happening: a new survey by Gallup finds both that a lot of people have gained insurance through the program and that the age mix of the new enrollees looks pretty good.

What was especially odd about the incessant predictions of health-reform disaster was that we already knew, or should have known, that a program along the lines of the Affordable Care Act was likely to work. Obamacare was closely modeled on Romneycare, which has been working in Massachusetts since 2006, and it bears a strong family resemblance to successful systems abroad, for example in Switzerland. Why should the system have been unworkable for America?

But a firm conviction that the government can’t do anything useful — a dogmatic belief in public-sector incompetence — is now a central part of American conservatism, and the incompetence dogma has evidently made rational analysis of policy issues impossible.

It wasn’t always thus. If you go back two decades, to the last great fight over health reform, conservatives seem to have been relatively clearheaded about the policy prospects, albeit deeply cynical. For example, William Kristol’s famous 1993 memo urging Republicans to kill the Clinton health plan warned explicitly that Clintoncare, if implemented, might well be perceived as successful, which would, in turn, “strike a punishing blow against Republican claims to defend the middle class by restraining government.” So it was crucial to make sure that reform never happened. In effect, Mr. Kristol was telling insiders that tales of government incompetence are something you peddle to voters to get them to support tax cuts and deregulation, not something you necessarily believe yourself.