Amid anticipation akin to a major sports event, the US Supreme Court begins hearing arguments Monday on President Barack Obama's landmark health reform, a case with huge implications for the nation and 2012 elections.
The nine justices of America's highest court meet for an unprecedented three days of arguments on different aspects of the constitutionality of the ground-breaking legislation.
The case has been polarizing for the United States: it would provide health insurance to some 32 million Americans lacking coverage, a major social accomplishment for some, but also would force people to buy insurance -- an intrusion into civil liberties for others.
Several hundred people gathered outside the court, some vying for a seat in the court to hear the history-making arguments, and others to march and chant and make speeches outside before banks of television cameras.
More than a hundred journalists filled alcoves in the marble columned court room, as members of bar, guests of the court and the public packed the remaining 330 seats.
The top US court has set aside six hours for oral arguments in the case, the longest in the past 45 years. Hearings typically last only about an hour.
Both supporters and opponents of the Affordable Care Act have been holding demonstrations to make their voices heard.
"It's health care for everybody. It's very important," said Jasper Johnson, a 26-year-old computer technician who came from San Francisco, and was among the handful of people camping out since Friday for the few seats set aside for the public to watch the start of the proceedings.
"I'm here not only for myself but for the economy as a whole."
But many Republicans oppose the measure, with frontrunning White House hopeful Mitt Romney calling the law an "unfolding disaster for the American economy."
The ruling could have enormous political ramifications, analysts say, especially if the court strikes down part or all of the reform.
Ilya Shapiro, a senior fellow for the conservative public policy foundation Cato Institute, said the case could cost Obama his job.
"If the law is struck down, then the administration's signature achievement is gone," Shapiro told AFP.
The law, enacted in 2010 but which will not come fully into force until 2014, is Obama's greatest accomplishment, realizing a long-held dream of generations of Democrats.
But Republicans seeking to thwart Obama's bid for a second term in the White House see it as an assault on individual liberties, and have vowed to repeal it if elected in the November presidential elections.
The main controversy focuses on a measure that requires all Americans to purchase personal health insurance from 2014 or face fines.
"If they can force you to buy health insurance, they can force you to buy a car, asparagus, a gym membership," said Kenneth Cuccinelli, attorney general of Virginia, one of 26 states seeking to overturn the law.
Other provisions bar insurance companies from refusing to insure people with pre-existing or chronic conditions, who are often now rejected for coverage or forced to pay exorbitant premiums.
The companies must also provide certain kinds of coverage that previously were excluded, such as contraception.
Opponents argue Congress exceeded its constitutional authority by approving the law.
The US Justice Department has hit back arguing the law is within the authority of Congress to regulate commerce and to tax citizens.
Senior White House adviser David Plouffe said the government's solicitor general, Donald Verrilli, "is going to put forward a very powerful case for why this law is constitutional and why it's important."
Backers say Americans who lack health care are less productive and often push their unpaid health bills onto taxpayers, who are forced to subsidize emergency room visits.
Paul Clement, a former solicitor general who will argue the other side for the 26 states challenging the law, says he will argue it is unprecedented and an "imposition" on citizens.
Because of the massive public interest, the court plans to release audio recordings of the debates on the same day as the hearings, which are expected to be packed with visitors in the marble-columned courtroom. Attorney General Eric Holder plans to attend.
Among the nine Supreme Court justices, five were appointed by Republican presidents and four by Democrats.
While a ruling is not expected until June, the justices must first decide whether they can rule on a law that has not yet taken effect. Then they must determine whether the health insurance requirement violates the constitution.
Some legal experts say that without the health insurance requirement, the entire law will be moot.
"Once you take the heart out of a body, it doesn't matter if the fingers can still move," said Michael Carvin, attorney for the National Federation of Independent Business.