America's Supreme Court is to rule on president Barack Obama's health care overhaul in a hearing that could shake the political landscape.
It will start proceedings in March and give its ruling a few months before the country decides if Mr Obama deserves another term.
This decision to hear arguments in the spring sets up an election-year showdown over the White House's main domestic policy achievement. And it allows plenty of time for a decision in late June, just over four months before election day.
The case could become the high court's most significant and political ruling since its 5-4 decision in the Bush v. Gore case nearly 11 years ago effectively sealed George W. Bush's 2000 presidential election victory.
The justices announced they will hear an extraordinary five-and-a-half hours of arguments from lawyers on the constitutionality of a provision at the heart of the law and three other related questions about the act. The central provision in question is the requirement that individuals buy health insurance starting in 2014 or pay a penalty.
The 2010 health care overhaul law aims to extend insurance coverage to more than 30 million Americans by requiring individuals to buy health insurance starting in 2014 or pay a penalty and other measures.
Republicans have called the Patient Protection and Affordable Care Act unconstitutional since before Mr Obama signed it into law in March 2010. But only one of the four federal appeals courts that have considered the health care overhaul has struck down even a part of the law.
In addition to deciding whether the law's central mandate is constitutional, the Supreme Court will also determine whether the rest of the law can take effect even if that central mandate is held unconstitutional. The law's opponents say the whole thing should fall if the individual mandate falls.
The administration counters that most of the law still could function, but says that requirements that insurers cover anyone and not set higher rates for people with pre-existing medical conditions are inextricably linked with the mandate and shouldn't remain in place without it.
Lastly, the justices will consider whether arguments over the law's validity are premature because a federal law generally prohibits challenges to taxes until the taxes are paid.