By Bill Mears
CNN Supreme Court Producer
WASHINGTON (CNN) -- It's the hottest ticket in town this week.
Two years and three days after President Barack Obama signed the Affordable Care Act into law, the Supreme Court is poised to offer the final word on the constitutionality of health care reform efforts.
Kicking off three days of oral arguments, the nine justices will begin debating the first of four separate questions Monday morning as the eyes of the nation turn to D.C. and insiders and the public jockey for a seat inside the court.
The justices know their eventual rulings could establish profound guidelines on the extent of congressional power and could shake up a presidential election year where health care has become a hot campaign topic.
"The social and political stakes just in this case in particular are quite significant, but even beyond that, there are broader constitutional principles," said Paul Clement, who will argue against the law before the justices. "This is a legal question and it's got a lot of people excited politically."
"The Affordable Care Act moves us very close to achieving health coverage for everyone," said Ron Pollack, executive director of Families USA, a health advocacy group. "It's my hope that the justices protect the law and allow the law to go into effect."
The public sessions start with 90 minutes of arguments on a legally dense, but nonetheless important, question.
It boils down to this question: Is the health care law's key provision a "tax" that could prevent the court from considering the broader constitutional questions? That provision is the "individual mandate" requiring most Americans to purchase some form of health insurance or face a substantial tax penalty.
An obscure federal law known as the Anti-Injunction Act, which dates back to 1867, bars claimants from asking for a refund on a tax until that tax has been collected and paid.
This "gateway" issue could stop the current legal fight in its tracks if the justices indeed think the minimum coverage requirement amounts to a tax.
In an unusual twist, the Obama administration is now siding with the law's opponents and will argue the mandate is not a tax. The high court actually designated a Washington private attorney, Robert Long, to argue in favor of the tax question.
Citing that 1867 law might give the court, particularly conservative members, a way out of deciding the explosive issue in an election year.
The majority could decide the political branches can best resolve the conflicts, at least for now, or that the matter can be handled after the November elections. Some court watchers have called this the health care "sleeper issue." It could potentially delay a decision on the constitutionality of the individual mandate for at least four years.
The larger, separate question of the individual mandate's constitutionality will be argued at the high court Tuesday.
Seats inside the court will be scare, both for interested parties and the public.
Individuals began lining up Friday morning for perhaps the 50 to 60 seats reserved for those on a first-come, first-serve basis.
The rest of the seats are assigned, requiring a special pass. Because of demand, the court's clerk has told representatives from Congress, the Obama administration, the states and the dozens of private advocacy groups to decide among themselves who will attend.
For example, 26 states are leading the legal challenge before the Supreme Court, but there will only be room for six attorneys general to attend the arguments. Legal sources said those negotiations over the choices turned testy, when some officials were not picked.
Sen. Max Baucus, D-Montana; Sen. Orrin Hatch, R-Utah; and U.S. Rep. Michele Bachmann, R-Minnesota, have revealed securing a precious seat.
Attorney General Eric Holder will lead the administration contingent.
And although it is little known, the justices themselves are allowed to give out up to nine tickets to anyone they want, so having an "in" with the bench might be the only way some interested parties will be admitted.
Dueling rallies and protests outside the court this week will add to what goes on inside the courtroom.
On Sunday, about a dozen people lined the sidewalk in front of the Supreme Court, along with their lounge chairs, blankets and umbrellas, hoping to obtain tickets.
Jill Andres has seen the court in action before. Andres attended hearings for the Wal-Mart discrimination case last year, and that experience has her excited to see history a second time around.
Andres said she is hoping to see the "insight into the nuances of the law that are interesting."
Others have made quite a trek to be in D.C.
"I'm here for myself and my family," said attorney Kathie Mcclure. She traveled from Atlanta and has been camping out since Friday to secure a seat into the courtroom.
"I'm interested in this issue because my kids are chronically ill. I have a son who has type 1 diabetes and a daughter who has epilepsy."
Frequently asked questions: A CNN guide to the arguments
Six lawyers will make their case in what is expected to be free-wheeling question-and-answer sessions characteristic of oral arguments. The main attorneys will be Clement on one side, representing the 26-state coalition opposing the law. Defending the law will be Solicitor General Donald Verrilli.
The public will be able to listen to the oral arguments on the court's website shortly after the sessions end.
The cases are Dept. of Health and Human Services v. Florida (11-398); National Federation of Independent Business v. Sebelius (11-393); and Florida v. Dept. of H&HS (11-400). Rulings are expected in June.
CNN's Casey Riddle and Greg Clary contributed to this report.