Five years ago, President Barack Obama signed a law that will be a significant part of his presidential legacy: the Affordable Care Act.

The U.S. Supreme Court will hear arguments on a case that will largely determine if that law is remembered as a success or failure. The court will decide if millions of Americans who have gotten insurance through the federal health care exchange qualify under the law for government subsidies to help pay for that coverage. If the court says they do not, those people will lose that federal assistance. Many won’t be able to pay for their insurance.

People who receive assistance through state-based exchanges would not be affected. Their status is clear under the law. But the impact on people in the 37 states that don’t have state exchanges would be profound enough that the underpinnings of Obamacare could collapse.

And then what? Health and Human Services Secretary Sylvia Mathews Burwell recently told the Senate Finance Committee that the administration has no Plan B if the court rules Obamacare does not permit subsidies for insurance received through the federal exchange.

Administration officials could try to press Congress to make a simple amendment to the law to allow subsidies via federal exchanges. It’s hard to see that succeeding, given Republican antipathy toward the law.

Administration officials could push those 37 states in which people rely on HealthCare.gov to build their own exchanges. That would restore eligibility for subsidies. But given the technical and political challenges, that’s unlikely to happen, at least quickly.

Congress could do nothing and watch millions of people lose health coverage. That’s the nuclear option.

Or Republicans and Democrats could set aside animosity and respond to a Supreme Court finding of a fatal flaw in Obamacare by coming up with an alternative.

The best blueprint we’ve seen — call it Plan B if you wish — comes from Republican Sens. Richard Burr of North Carolina and Orrin Hatch of Utah, and Rep. Fred Upton of Michigan.

Their proposal, called the Patient CARE Act, strips away much of Obamacare’s overreach. Individuals would not be required to buy coverage or pay a penalty. Employers wouldn’t be required to provide coverage or pay a penalty. Taxes that prop up Obamacare, including the 2.3 percent medical device tax on sales of hip implants, MRI machines, heart valve replacements and other equipment, would be rescinded.

Two widely liked Obamacare benefits would remain in law. Insurers couldn’t deny coverage because of pre-existing conditions and young adults could stay on their parents’ plan until age 26.

Individual responsibility would be rewarded. People who buy insurance would be guaranteed continuous coverage, but people who seek coverage only after they’re sick or injured could be charged higher premiums.

Consumers would have more flexibility in choosing insurance. The color-coded benefit levels would be scrapped in favor of a robust, state-regulated marketplace that would free insurers to offer a wider range of plans. Companies could tailor policies to fit consumers’ needs and their pocketbooks, not federal government dictates of what “good” coverage includes.

Many Americans would still get help to pay premiums, though subsidies would not be as extensive as they are under Obamacare. A family of four earning up to about $72,000 a year would qualify for help through tax credits. People who buy insurance on the individual market would get a tax break similar to the break enjoyed by people who get coverage through an employer.

A recent analysis by the nonpartisan Center for Health and Economy concluded that 4 million fewer people would be covered under the Patient CARE Act than under Obamacare. But remember — if the Supreme Court finds federal exchange subsidies are illegal, Obamacare coverage will be greatly constricted. The Center for Health and Economy also found the Patient CARE Act would help tame medical costs and yield an estimated net savings to the Treasury of roughly $530 billion over a decade, compared with the current law.

Republicans rightly expressed surprise that the Obama administration isn’t preparing a Plan B. There’s a good chance the Supreme Court will find that federal exchange subsidies violate the letter of the Affordable Care Act. The constructive thing to do now: Get over the years of Obamacare political warfare and start preparing for an adverse court ruling.

Burr-Hatch-Upton could be the framework for Plan B, as in bipartisan.

The above editorial appeared in the Chicago Tribune on Feb. 27