In the first Affordable Care Act case three years ago, the Supreme Court had to decide whether Congress had the power, under the Commerce Clause or some other source of authority, to require individuals to buy health insurance. It was a question that went directly to the structure of American government and the allocation of power within the federal system.
The court very nearly got the answer wrong with an exceedingly narrow reading of Congress’s commerce power. As everyone remembers, Chief Justice John G. Roberts Jr., himself a member of the anti-Commerce Clause five, saved the day by declaring that the penalty for not complying with the individual mandate was actually a tax, properly imposed under Congress’s tax power.
... the new Affordable Care Act case, King v. Burwell, to be argued four weeks from now, is different, a case of statutory, not constitutional, interpretation. The court has permitted itself to be recruited into the front lines of a partisan war. Not only the Affordable Care Act but the court itself is in peril as a result.
At the invitation of a group of people determined to render the Affordable Care Act unworkable (the nominal plaintiffs are four Virginia residents who can’t afford health insurance but who want to be declared ineligible for the federal tax subsidies that would make insurance affordable for them), the justices have agreed to decide whether the statute as written in fact refutes one of the several titles that Congress gave it: "Quality, Affordable Health Care for All Americans."
If the Supreme Court agrees with the challengers, more than seven million people who bought their insurance in the 34 states where the federal government set up the marketplaces, known as exchanges, will lose their tax subsidies. The market for affordable individual health insurance will collapse in the face of shrinking numbers of insured people and skyrocketing premiums, the very "death spiral" that the Affordable Care Act was designed to prevent.
You should read the full analysis by Greenhouse, including a summary of and links to some of the briefs filed on behalf of the government here.