If the Supreme Court breaks down along its usual ideological lines on the vote on the health care law, Justice Anthony Kennedy -- known as the swing vote on the court -- could be the one to decide whether the government can require almost every American to buy health insurance or pay a fine.
When the court hears the case on the Affordable Care Act in March, advocates, experts and the media will parse every question from Kennedy, hoping for a hint of his views on the merits of the case.
The central focus will be on the individual mandate, the key provision that requires individuals to buy health insurance by 2014 or pay a tax penalty.
As its principal argument that Congress has the authority to enact the mandate, the administration relies on the Commerce Clause of the Constitution that says in part: "The Congress shall have power ... to regulate commerce with foreign nations, and among the several states and with the Indian tribes."
Critics of the health care law argue that while Congress has substantial power to regulate interstate commerce, it may not compel people into the marketplace and force them to buy a product.
Paul D. Clement, a lawyer from Bancroft PLLC, who is representing the 26 states challenging the law, writes in court briefs, "In the over 200 years that Congress has sat, it has never before attempted to exercise its Commerce Clause power in this manner."
Kennedy, 75, who was appointed to the court in 1988 by Ronald Reagan, has often been the deciding vote in big cases. But the Supreme Court has never heard a case quite like the challenge to the Affordable Care Act, and predictions regarding the final vote count have varied significantly.
Many were surprised when two appellate court judges, with sterling reputations in conservative circles, voted to uphold the constitutionality of the mandate when a similar challenge came before their courts.
The case -- with an unprecedented 5½ hours of argument allotted to it -- could defy expectations.
Justice Kennedy the Swing Vote
Scholars have scoured Kennedy's previous cases for hints on how he might rule. They point out that it's not always easy to forecast Kennedy's vote on particular cases and that the term "swing vote" can be misinterpreted.
"I would reject equating swing vote with lack of clarity," says Michael C. Dorf, a professor at Cornell University Law School and a former Kennedy law clerk. "Being the swing vote is simply an artifact of who the other eight justices are. On some issues, free speech for example, he's very liberal. On gay rights, he's been very liberal, out ahead of the court. On other issues, he's been conservative -- the Establishment Clause, for example," which prohibits a national religion for the United States.
Neil S. Siegel, a professor at Duke Law, says Kennedy "cares about a number of different things and oftentimes they are conflicting. He cares about robust federal power to regulate markets, he cares about robust federal power to create and maintain an integrated national economy. But at the same time that he cares about federalism, he cares about states' power. He cares about individual liberty, and the role that federalism plays in preserving it."
"I think it's fair to say he resists absolutes in most areas of the law. That makes him a little less easy to pigeonhole," Dorf says.
Although previous Supreme Court cases regarding guns in schools, violence against women and medical marijuana may seem far afield of the health care debate, they offer insight into Kennedy's views on the scope of congressional power.
Lopez and Morrison
From 1937 until 1994, the court upheld Congress' broad power to legislate pursuant to the Commerce Clause.