Jon Cohn considers whether the Affordable Care Act will still work if the Supreme Court strikes down the mandate but leaves everything else untouched:

The Congressional Budget Office projects that the Affordable Care Act would, without a mandate, lead to about 16 million people getting health insurance relative to the number who would have it if reform never took effect at all. Estimates from researchers at the Rand Corporation and Urban Institute, as well as MIT economist Jonathan Gruber, project similar coverage gains, although they differ in the details. (It’s worth noting that a few experts, including some of Obama’s original campaign advisers, have never thought the mandate was essential as CBO and the other researchers do.) ...

In other words, the best available evidence suggests that the law without a mandate would fall significantly short of the law with a mandate, both in terms of reach and stability. From a constitutional standpoint, that should be more than enough to make it “necessary and proper” to the government’s (clearly constitutional) task of providing affordable coverage to all. And yet ... even without the mandate, the law would likely bring insurance to more people than have insurance today, while bolstering coverage for people who already have it. From a budget standpoint, the government might even spend less money overall, since it’d be assisting so many fewer people.

One important caveat: If the federal mandate falls and Congress doesn’t provide a patch, various states might choose to impose their own mandates or some other set of policies that take the place of the mandate. So it might be somewhat less either/or than this analysis suggests.

That said, a related question is which outcome sets up the best political incentives for the system to evolve back into something functional.

If the Supreme Court overturns the mandate but leaves the insurance regulations, that will badly damage the law, as Cohn says, but it will also force insurers to lobby aggressively for some kind of patch. That could potentially lead to reform of the now-gutted reforms more quickly. On the other hand, it will also lead to high premiums and a clearly dysfunctional law, which could turn the public sharply against it.

If SCOTUS overturns all the insurance regulations, which is the Obama administration’s preferred approach to “severability,” it will mean the most popular part of the bill — the end to discrimination based on preexisting conditions — is gone. That might clarify the stakes in the mind of the public, and you could imagine subsequent pressure on politicians to come up with alternatives. But it would also leave insurers with more customers but few new rules, and it’s easy to imagine them using their muscle to protect this unexpectedly wonderful situation.

If SCOTUS overturns the whole law, or upholds the whole law, all these considerations are, of course, moot.