Another assumption the insurers made was that a bailout would be politically sustainable. That assumption will also be tested. Obamacare has always depended, both operationally and politically, on an alliance between the administration and insurance companies. But that alliance is vulnerable. The most controversial element of Obamacare to date — the coercive measures it includes to get people to buy insurance — is only there to protect the insurance companies’ viability. A bailout could be just as unpopular a sop to the insurers.

Senator Marco Rubio, a Florida Republican, has introduced a bill to repeal the risk-corridors provision. Its passage would be preferable to a bailout, but it would make more sense to eliminate taxpayer exposure altogether. Let companies in the exchanges subsidize each other, and leave the rest of us out of it.

Insurers are already screaming about Rubio’s proposal, desperate to keep Obamacare’s subsidies even as they ask for relief from its regulations. If Rubio’s bill or something like it passes, they would have to raise premiums and thus make their plans even more unattractive than they already are — or just withdraw from the exchanges. Obamacare would, in other words, become even less likely to succeed than it already is.