The most important change in the bill, however, is the way it would effectively gut protection for people with pre-existing medical conditions. The Affordable Care Act put minimum standards on the kinds of policies insurers were allowed to offer; the new Senate bill gives in to demands by Ted Cruz that insurers be allowed to offer skimpy plans that cover very little, with very high deductibles that would make them useless to most people.

The effects of this change would be disastrous. Don’t take my word for it: It’s what the insurers themselves say. In a special memo, AHIP, the insurance industry trade group, warned against adopting the Cruz proposal, which would “fracture and segment insurance markets into separate risk pools,” leading to “unstable health insurance markets” in which people with pre-existing conditions would lose coverage or have plans that were “far more expensive” than under Obamacare.

Or to put it another way, this bill would send insurance markets into a classic death spiral. Republicans have been predicting such a spiral for years, but keep being wrong: All indications are that Obamacare, despite having some real problems, is stabilizing, and doing pretty well in states that support it. But this bill would effectively sabotage all that progress.

And let’s be clear: Many of the victims of this sabotage would be members of the white working class, people who voted for Donald Trump in the belief that he really meant it when he promised that there would be no cuts to Medicaid and that everyone would get better, cheaper insurance. So why are Republican leaders pushing this? Why is there even a chance that it might become law?

The main answer, I’d argue, is that what would happen if this bill passes — a big decline in the number of Americans with health insurance, a sharp reduction in the quality of coverage for those who keep it — is what Republicans have wanted all along.

During the eight-year jihad against the Affordable Care Act, of course, the G.O.P. pretended otherwise: denouncing Obamacare for failing to cover everyone, attacking the high out-of-pocket expenses associated with many of its policies, and so on. But conservative ideology always denied the proposition that people are entitled to health care; the Republican elite considered and still considers people on Medicaid, in particular, “takers” who are effectively stealing from the deserving rich.

And the conservative view has always been that Americans have health insurance that is too good, that they should pay more in deductibles and co-pays, giving them “skin in the game,” and thus an incentive to control costs.

So what we’re seeing here is supposed to be the last act in a long con, the moment when the fraudsters cash in, and their victims discover how completely they’ve been fooled. The only question is whether they’ll really get away with it. We’ll find out very soon.