What happens if the Supreme Court loses legitimacy?

It appears well within the realm of plausibility that five justices of the Supreme Court have already decided to trash the Affordable Care Act by means of a preposterous legal maneuver. Paul Krugman discusses it here, and attorney Neil Seigel says pretty much the same thing here. So you have the perspectives of an economist, and a lawyer.

They, and many other sober observers, find the reasoning of the DC Circuit panel in Halbig v. King absurd. It will be reversed by the full court, and it has been resoundingly rejected by all other federal courts. The Supreme Court does not need to hear the case. Why have they chosen to do so?

As all our readers presumably know, the ACA has three main components, all of which are essential for it to work. It requires insurance companies to cover everybody for the same price, with an adjustment for age, regardless of their current or former state of health. In other words, you can't be denied coverage or charged a fortune because of pre-existing conditions. (That's called guaranteed issue and community rating, BTW.) However, if you do that, there's a danger that people won't bother buying insurance until they get sick. You need those healthy people in the pool to keep it affordable for everybody. Hence the individual mandate. Again, however, not everybody can afford insurance, so you have subsidies for moderate income people. (We'll leave the Medicaid expansion aside for now.)

The literal language of the ACA says the subsidies are available to people who buy insurance through "exchanges established by the state." But Republican governors refused to establish exchanges in many states, so the federal government stepped in on their behalf. Elsewhere in the ACA this is clearly intended and the federally run exchanges are fully the equivalent of state-run exchanges. It's just slightly ambiguous language, but the intent of the statute is clear. Yet Halbig claims that people who get insurance through federally-run exchanges aren't eligible for the subsidies.

Krugman and Seigel both state, quite boldly, in their own ways, that if the court buys this absurdity it will prove that conservative jurisprudence is not about upholding the law, or any theory of law; it is purely political, adopting any form of sophistry in order to further the conservative political movement and the interests of the Republican party. That millions of people will lose their access to health care, and many of them will die, would apparently mean nothing to Scalia and Alito.

But what happens to the American polity if half of us are forced to conclude that the Supreme Court is a fundamentally illegitimate institution? I hope John Roberts is thinking about that.