by Kimberley Strassel

Pure, unadulterated political gifts don’t come often to Washington, and even when they do their recipients are often too busy inspecting the horse’s mouth to make use of them. The miracle gift this season is King v. Burwell, and next week will show whether Republicans have the wit to unify around an effective strategy to dismantle ObamaCare.

That health law has been on the books about 1,800 days, and the GOP has had nearly as many responses. Replace, repeal, delay, defund, strategic dismantlement, government shutdown, hearings, subpoenas, coaxing, tantrums. Nothing has worked. And now along comes a lawsuit that few noticed but offers the Supreme Court the opportunity this summer to strike down the payment of government subsidies (and in the process dismantle the individual and employer mandate) in the 37 states that have a federal exchange.

Conservatives risk an epic mistake in thinking that striking down subsidies through a federal exchange marks the end of ObamaCare. But it is an opening to finally get behind a plan that will. The Obama administration is already mounting an aggressive campaign to keep or restore the status quo. The White House’s refusal to elucidate a Plan B is its first step, a warning to the Supreme Court that it risks causing mass disruption in the health-care market.

If the Supremes strike down the subsidies anyway, President Obama will be instantly on a stage, explaining that an activist court, at Republican bidding, stole health care from six million Americans. He’ll be flanked by dozens who lost subsidies and tell stories of cancer and bankruptcy. He’ll ask if Republicans really are willing to deny little Tommy chemo—out of a base desire to obstruct him—when they could make an easy and permanent fix by changing a few, tiny words in the law. He’ll pressure GOP governors to default to bad ideas that will effectively reinstate his policies.

Some conservatives would ignore this threat. They believe it is enough to say that this is a question of rule of law, that it is on Mr. Obama to live with his mess. The fantasy is that the public will rise up and force the president to repeal his signature achievement. Others are wary of any alternative that helps those who lost subsidies, on the grounds that it amounts to Republicans endorsing permanent ObamaCare-lite.

These positions underestimate the president’s resolve and the public backlash against Republicans for doing nothing. Independent Women’s Voice, run by Heather Higgins (who also heads up the repeal pledge), recently completed a study with likely voters about the court case and subsidies. While a majority cheered the idea of a ruling against ObamaCare, they also said it was very important that those harmed receive some help.

Bear in mind, too, that many of the 37 states without a state exchange are Republican strongholds, run by GOP governors who did the right thing by refusing to run their own exchange and now deserve better than to be left high and dry.

The do-nothing approach also sets Republicans up to blow the best opportunity they may ever have to act like health-care leaders and begin a transition to a free market. They can continue to beat their heads on the repeal wall, and cross their fingers for a Republican president and Congress in 2016. Or they can use the court decision to craft and message a policy that makes a difference now.

Most urgent is simply getting out a conservative plan to reassure the Supreme Court that there is one. That’s going to happen in the coming days, as working groups in both the Senate and House—and some individual members—release their own backup proposals. Those involved are still mulling over final policy proposals, but the good news is that they seem to be solidifying around some key principles: Knocking back the rules and mandates that make ObamaCare expensive, giving the states more flexibility and opt-outs, and offering targeted, temporary and more free-market options for those who will lose insurance.

A response along these lines gives Republicans a more powerful message than that of the president. They can point out that the court saved at least 50 million Americans from the costs of the individual and employer mandate. They can offer to save the six million more who are in dire straits because Democrats and insurance lobbyists wrote an unworkable law. They can offer Americans health care that is more affordable, simpler and with more choices. They can point out the alternative is the restoration of the Obama way—health-care rule by executive order.

And they can dare the president to stand in the way of a credible fix, in the face of five years of public disapproval of his mess of a law.

Their other option is to go 20 rounds over strategy and policy—to demand all or do nothing (a strategy that’s working out so well with immigration). If they miss this ObamaCare exit ramp, they might not get another.