WASHINGTON -- The U.S. Supreme Court could hand down a momentous decision as early as Monday on the massive overhaul of America's health care system _ a ruling in the heat of the U.S. presidential election that might strike down President Barack Obama's key legislative achievement.
Republicans, including presumptive nominee Mitt Romney, would get a significant political boost should the conservative-dominated high court find all or part of the health care law unconstitutional.
Romney has joined his party in promising to revoke the health care overhaul, even though the Obama law took its inspiration from one that went into effect in Massachusetts when Romney was governor.
The central issue before the court is the overhaul's requirement that all Americans have health insurance coverage or face a federal fine.
The law is constructed so that its provisions that will extend coverage to tens of millions of uninsured Americans. That will be financed by vastly expanding the insurance market _ mainly by forcing young, healthy people to buy insurance, thus spreading the risk for insurance companies.
The court could allow the law to stand as is or strike down individual provisions like the insurance coverage mandate. All outcomes short of finding the law fully constitutional would produce an upheaval in the health care sector that has been working toward implementation of the big changes already in place or coming into effect two years from now.
Because the Affordable Care Act is so complicated, an orderly unwinding would prove difficult if it were overturned entirely or in part.
Better Medicare prescription benefits, currently saving hundreds of dollars for older people with high drug costs, would be suspended. Medicare is low-cost government health care for Americans when they reach age 65. The same would go for full coverage for preventive care that is now available to retirees and working families alike.
Partially overturning the law could leave hospitals, insurers and other service providers dealing with tax increases and spending cuts without the law's promise of more paying customers to offset losses.
If the law is upheld, other complications could result.
The nation is so divided politically that states led by Republican governors and legislatures are largely unprepared to carry out critical requirements such as creating insurance markets.
"At the end of the day, I don't think any of the major players in the health insurance industry or the provider community really wants to see the whole thing overturned," said Christine Ferguson, a health policy expert who was commissioner of public health in Massachusetts when Romney was governor.
"Even though this is not the most ideal solution, at least it is moving us forward, and it does infuse some money into the system for coverage," said Ferguson, now at George Washington University.
While it's unclear how the justices will rule, oral arguments did not go well for the Obama administration, especially on the central issue of requiring all Americans have insurance.
That mandate takes effect in 2014, at the same time that the law would prohibit insurance companies from denying coverage to people with existing health problems. Most experts say the coverage guarantee would balloon costs unless virtually all people joined the insurance pool.
Opponents say Congress overstepped its constitutional authority by issuing the insurance mandate. The administration says the requirement is permissible because it serves to regulate interstate commerce. Most people already are insured. The law provides subsidies to help uninsured middle-class households pay premiums and expands Medicaid, federal health care for poor people, to expand that program.
A mixed verdict from the high court would be the most confusing outcome. Some parts of the law would be struck down while others lurch ahead.
That kind of result would seem to call for Congress to step in and smooth any necessary adjustments. Yet partisan divisions on Capitol Hill are so intense that hardly anyone sees a chance that would happen this year.
Associated Press writer Ricardo Alonso-Zaldivar contributed to this report.