The legal challenge highlights two fundamentally different views of the role of government. The decision will affect the lives of hundreds of millions of Americans and could also help decide the November presidential election.
Jan Crawford reports from outside the Supreme Court that what's at stake in the decision is the fate of the requirement that nearly all Americans, from birth until death, must have health insurance or pay a penalty - the so-called "individual mandate."
If the court strikes down the mandate, then it has to figure out what to do with the rest of the massive, 2,700-page law.
Norah O'Donnell reports from the White House that the president's advisers expressed confidence Thursday morning. Mr. Obama and Vice President Joe Biden are expected to be together in the Oval Office when the court hands down its ruling. The president is expected to address the nation after the court rules.
Regardless of what the justices decide, the decision is expected to have significant political ramifications. This is the president's signature piece of legislation from his first term.
The president has argued that the law provides millions of Americans with consumer protections, such as providing access to preventative care and preventing insurance companies from discriminating against those with pre-existing conditions.
Former Massachusetts Gov. Mitt Romney, Mr. Obama's Republican opponent in the presidential race, has said he will repeal whatever remains of the health care reform law on the first day of his administration should he be elected president.
On Capitol Hill, Nancy Cordes reports Democrats and Republicans have been honing their messages for weeks on how to respond to the court upholding the law or striking it down. All of the more than 200 House Republicans will go into a closed-door meeting once the decision comes down to pore over it and discuss exactly how they want to react to it.
One thing neither side is doing is crafting legislation to replace the law if some or all of it gets struck down. That's because Democrats continue to insist that it will be upheld and because Republicans say they want to move slowly and won't introduce any new legislation until after the November elections.
However, if the justices throw out the individual mandate but keep some of the law's perks, economists have predicted that insurance premiums could skyrocket quickly, so Congress may be forced to deal with this issue between now and the elections.