But would it? Given the awful mess such a ruling would create, why wouldn't Congress and the White House instead repeal the entire law and put an end to the hemorrhaging?
Much depends on how the public and elected officials react to millions of Americans losing their subsidies and health insurance in up to 37 states, throwing the insurance markets in those states into chaos. Republican governors and lawmakers in at least some of those states might establish state-run exchanges to keep the subsidies flowing.
The GOP-controlled Congress might take action to extend or restore the subsidies.
These politicians—including some who plan to run for president in 2016—may face powerful pressure from consumers, hospitals, physicians and insurers affected by the coverage disruption to fix the problem.
A recent Wall Street Journal/NBC News poll found that 54% of Americans say that if the Supreme Court throws out the subsidies, Congress should pass a law to restore financial help to enable people to keep their health insurance.
But then again, ideology is a powerful thing. There is no good reason to think that Republicans who have repeatedly vowed to kill the Affordable Care Act would step in to save it.
Lots of Washington observers say there is little or no chance congressional Republicans would even be able to agree among themselves on any extension or replacement plan.
If people in all those states lost their subsidized coverage and the insurance markets went into a death spiral, it's almost certain that many Republicans in the powerful tea party wing would call for Congress to repeal the entire law. They would argue that functioning insurance markets could not be restored as long as the ACA requirements remained in place mandating insurers to accept all applicants regardless of health status, provide standard comprehensive benefits, and charge older customers only three times more than young enrollees.
And there's no assurance that weak-kneed congressional Democrats, facing a political uproar in their states, wouldn't go along with a repeal vote. After all, many have shrunk from wholeheartedly supporting the law, particularly at election time. If enough panicked Democrats defected and joined Republicans in a repeal vote, they could override almost certain veto by President Barack Obama.
Pressure for repeal would be heightened because after the tax credits were wiped out, residents of the affected states—mostly red states—would be left subsidizing, through their tax dollars, the mostly blue states that have their own exchanges and whose residents would keep their tax credits. On top of that, the lower-middle and middle-class Americans losing their tax credits in the affected states might well resent that lower-income people in 28 states who earn up to 138% of the federal poverty level would continue receiving coverage under the ACA's Medicaid expansion.
“If the Supreme Court rules against the Obama administration in King and these states (without their own exchange) don't decide to change their stance on Obamacare, then they will be massively subsidizing the other two-thirds of the country,” Ezra Klein wrote in Vox. “They will be paying for Obamacare and getting nothing for it.
But one veteran observer of U.S. healthcare politics thinks Republicans would feel irresistible political pressure to find some face-saving way to preserve Obamacare's premium subsidies.
If the subsidies are eliminated and the insurance markets go into a death spiral, “the problems will hit in Republican-governed states,” says Theda Skocpol, a Harvard University government and sociology professor who wrote a 1996 book, Boomerang, about why the Clinton healthcare reform effort failed in the 1990s. “That's a very important part of the equation in who will feel pressure to do something and who's likely to get the blame if something's not done to fix things.”
Skocpol and University of Minnesota political science professor Lawrence Jacobs recently wrote that Republican governors in Indiana, Iowa, Michigan, Nevada, New Jersey, North Dakota and Ohio would face immediate dilemmas because they would have to explain why poor people in their states would continue to receive coverage (PDF) through the Obamacare Medicaid expansion while middle-income residents would lose their subsidized insurance.
In addition, Skocpol points out that likely Republican presidential candidates Jeb Bush, Chris Christie, Mike Pence and Scott Walker all would have to explain why hundreds of thousands of their states' middle-class residents lost their health insurance because of a Republican-supported lawsuit.
Going into the 2016 elections, she argues in an interview, it would be much better for Republicans politically if the Supreme Court upholds the ACA premium subsidies. “If the court takes away subsidies from millions of people in Republican-led states,” she says, “that will hand the Democrats a perfect issue for the 2016 presidential and Senate races.”
She thinks Chief Justice John Roberts will have the following conversation in his own mind with Republicans as he wrestles with whether to provide the deciding vote in the King case to strike down the subsidies:
“Why should I go down in history aligning my court in such a blatantly partisan way as the destroyer of subsidized coverage for millions of Americans and weakening executive branch powers in the process?” Skocpol imagines Roberts saying to his fellow conservatives. “Why don't all of you get yourselves together, elect a Republican president in 2016, and do this yourselves?”
(This blog post has been updated.)
Follow Harris Meyer on Twitter: @MHHmeyer