Medicare went through the same cycle. Before it was enacted, Ronald Reagan warned that it would bring socialism and “invade every area of freedom as we have known it in this country.” Today, Medicare has overwhelming public support, so much so that Republicans attacked the A.C.A. with the (false) claim that it would steal money from Medicare.

And this gets at the heart of conservative opposition to social safety-net programs: It’s not about the belief that they will fail, but about fear that they will succeed, and in so doing become irreversible — which means that they must be stopped before they can start showing results.

So it has been with Obamacare. Before 2014, when the program went fully into effect, conservatives were quite successful at turning public opinion against it. It would lead to “death panels”; it would lead to “rate shock”; it would cause the budget deficit to balloon.

But public opinion has shown a steady turnaround since then. The share of voters believing that it’s the government’s responsibility to ensure that all Americans have health coverage has shot up since its 2014 nadir. Approval of the A.C.A., while still not overwhelming, has shown a more or less steady upward trend.

When Republicans held town halls over A.C.A. repeal last year, they were shocked by the intensity of public opposition. And elections, both state elections like Virginia’s and special elections for Congress, keep showing that trying to roll back coverage is a big political loser.

Again, you might think this would lead the G.O.P. to drop the whole issue. And if Republicans lose the House this November, they probably will, and America will become like every other advanced country: a society in which access to essential health care is considered a basic right.