What happens if the Supreme Court overturns the Patient Protection and Affordable Care Act? In some ways, very little: The architects of the constitutional case against the law designed their argument as a precision-guided missile that would take out ObamaCare while leaving the surrounding legal and policy edifice standing. Politically, however, a ruling against ObamaCare could have a huge effect on the health policy debate.

A decision against the law probably will not herald a sea change in the way the Court interprets the Constitution. Much case law and scholarship will still support the notion that the Commerce Clause gives Congress sweeping power to regulate economic activity of all kinds. The "substantial effects" doctrine would still allow Congress to restrict individual choices that are said to have ripple effects on interstate commerce.

Nor would a negative ruling have a major impact on the nation's entitlement infrastructure. A few provisions from the law that have already been enacted would be wiped from the books, and Medicare's budget baseline would revert to its previous state. But since the law's major coverage provisions have not kicked in yet, most Americans would not notice the change.

Would health policy simply return to its pre-2010 state? Yes, but with one major difference: ObamaCare would be discredited, legally and politically —potentially clearing a path to more effective health care reforms.

In the years prior to ObamaCare's passage, Democrats and their allies tirelessly built a policy consensus around a major overhaul of the American health care system based on universal coverage. As Barack Obama swept to victory in the 2008 election, advocates of universal coverage settled on a patchwork approach: mandate, regulate, and subsidize, while claiming to reduce the federal budget deficit.

But with the insurance mandate off the table, that policy consensus will no longer exist. ObamaCare's consistently negative poll numbers—roughly half the public has opposed the law since its passage, and two-thirds oppose the mandate—will further complicate matters. Many moderate Democrats were worried about both the political and fiscal costs of health care reform to begin with. The combination of a Supreme Court defeat and widespread opposition will reinforce their resistance not only to ObamaCare's specific reforms but to any large-scale health care overhaul. Liberal reformers determined to foist major structural changes onto the health care system will no longer have a viable short-term battle plan.

While those forces regroup, the free market policy community can build a case and consensus around less expensive, less intrusive, and more effective reforms. Granted, this won't be easy; one of the reasons ObamaCare passed was that opponents spent too little time and effort on crafting workable alternatives. In the last two years, Republicans chanting "repeal and replace" have focused far more energy on the former part of the slogan.

But even if those efforts are only minimally successful, policy will still be moving in a favorable direction—away from expensive, expansive, top-down projects and toward consumer-driven reforms. Congress has taken up a major health care reform, on average, about once every 18 years. Each time, the reforms have been marginally more market friendly. Far from clinching the case for a government-run single-payer system, as some progressives hope, overturning ObamaCare would clear the legislative and political slate, making way for choice-based reforms that tackle rising health care costs without adding yet another expensive entitlement.

The health policy war, in other words, would be far from over, but scrapping ObamaCare would be a significant victory.

Peter Suderman is a senior editor at reason.