A: That would settle the legal argument but not the political battle.

The clear winners if the law is upheld and allowed to take full effect would be uninsured people in the United States, estimated at more than 50 million.

Starting in 2014, most could get coverage through a mix of private insurance and Medicaid, a safety-net program. Republican-led states that have resisted creating health insurance markets under the law would have to scramble to comply, but the U.S. would get closer to other economically advanced countries that guarantee medical care for their citizens.

Republicans would keep trying to block the law. They hope to elect Mitt Romney as president, backed by a GOP House and Senate, and repeal the law, although their chances of outright repeal would seem to be diminished by the court's endorsement.

Obama would feel the glow of vindication for his hard-fought health overhaul, but it might not last long even if he's re-elected.