By Eugene Robinson - March 30, 2012

WASHINGTON -- In arguments before the Supreme Court this week, the Obama administration might have done just enough to keep the Affordable Care Act from being ruled unconstitutional. Those who believe in limited government had better hope so, at least.

If Obamacare is struck down, the short-term implications are uncertain. Conservatives may be buoyed by an election-year victory; progressives may be energized by a ruling that looks more political than substantive. The long-term consequences, however, are obvious: Sooner or later, a much more far-reaching overhaul of the health care system will be inevitable.

To say the least, the three days of oral argument before the high court did not unfold the way many experts had expected. Confident predictions that the administration would prevail by a lopsided margin became inoperative as soon as the justices began pummeling Solicitor General Donald Verrilli with pointed questions.

At one point on Wednesday, as the barrage was winding down, Chief Justice John Roberts told Verrilli he could have an extra 15 minutes to argue a point. Verrilli replied, "Lucky me."

In the end, however, Verrilli gave the skeptical justices what they were looking for: a limiting principle that allows them, should they choose, to defer to Congress and uphold the law.

At the heart of the legislation is the requirement that individuals purchase health insurance or pay a fine. It became clear by their questioning that the court's five conservatives -- including Justice Anthony Kennedy, the swing vote who sometimes crosses the ideological divide and votes with the liberals -- see this mandate as a significant expansion of the federal government's reach and authority.

Verrilli argued that the mandate is permissible under the clause of the Constitution giving the government the power to regulate interstate commerce. Justices demanded a limiting principle: Where does this authority end? If the government can compel a citizen to buy health insurance, why can't it compel the purchase of other things?

Justice Antonin Scalia raised the specter of an all-powerful government that could even "make people buy broccoli" if it wished. Scalia's mind seemed to be made up, but Kennedy seemed to be genuinely looking for a principle that permitted a health insurance mandate but not a broccoli mandate.

And Verrilli gave him one. The market for health insurance is inseparable from the market for health care, he argued, and every citizen is a consumer of health care. Those who choose not to buy health insurance require health care anyway -- often expensive care at hospital emergency rooms -- and these costs are borne by the rest of us in the form of higher premiums.

I think Verrilli made his case. The court is supposed to begin with the assumption that laws passed by Congress are constitutional. Justices don't have to like the Affordable Care Act in order to decide it should remain in effect. If some members of the court think they could do better, maybe they should quit and run for legislative office.

But it's going to be a close call. What if they strike down the law?

The immediate impact will be the human toll. More than 30 million uninsured Americans who would have obtained coverage under Obamacare will be bereft. Other provisions of the law, such as forbidding insurance companies to deny coverage based on pre-existing conditions and allowing young adults to remain on their parents' policies, presumably would also be invalidated; if not, they would have to be modified to keep insurance rates from climbing sharply. The United States would remain the only wealthy industrialized country where getting sick can mean going bankrupt.

Eventually, however, our health care system will be restructured. It has to be. The current fee-for-service paradigm, with doctors and hospitals being paid through for-profit insurance companies, is needlessly inefficient and ruinously expensive.

When people talk about out-of-control government spending, they're really talking about rising medical costs that far outpace any conceivable rate of economic growth. The conservative solution -- shift those costs to the consumer -- is no solution at all.

Our only choice is to try to hold the costs down. President Obama tried to make a start with a modest approach that works through the current system. If this doesn't pass constitutional muster, the obvious alternative is to emulate other industrialized nations that deliver equal or better health care outcomes for half the cost.

I'm talking about a single-payer health care system. If the Supreme Court strikes down Obamacare, a single-payer system will go from being politically impossible to being, in the long run, fiscally inevitable.