Once the conservative legal strategy that gave rise to King v. Burwell got off the ground, Republicans in Congress probably had no choice but to become cheerleaders for, or active participants in, the ensuing litigation.

The imminence of the decision in the Obamacare challenge, expected from the Supreme Court sometime this month, is exposing the terrible predicament the entire strategy created for the party.

The problems Republicans will encounter if they win King—eliminating billions of dollars worth of insurance subsidies—are fairly clear and have been detailed at length. But it is also quite conceivable that the whole effort will boomerang on the GOP even if the government wins in King, and the federal subsidies survive for those states using federally facilitated exchanges. A number of persuasive legal arguments point to a victory for the government. But one of the most likely paths begins with the Court concluding that the Affordable Care Act statute is ambiguous—that both parties’ readings of the law are plausible—and that deference should go to the government.

As Chief Justice John Roberts suggested with his one and only question at oral arguments, this would leave the door ajar for a future presidential administration to reinterpret the statute, and discontinue the subsidies.

It’s difficult to fathom that any Republican president would turn off the subsidies quite as abruptly as the challengers want the Court to do. But if the government wins in this way—on what's known as the second step of the Chevron deference standard—it will create a new conservative litmus test for Republican presidential candidates. If elected, will you shut down the subsidies? I suspect most of the candidates will yield to pressure from the right and promise to do precisely that. Most immediately, this promise becomes a general election liability for the Republican primary winner. If that person becomes president, it will turn into an administrative and political nightmare, forcing states and the U.S. Congress to grapple with a completely elective policy fiasco.