The Supreme Court on Thursday upheld the individual health-insurance mandate that is at the heart of President Obama’s landmark health-care law, saying the mandate is permissible under Congress’s taxing authority.

The potentially game-changing, election-year decision — a major victory for the White House less than five months before the November elections --will help redefine the power of the national government and affect the health-care choices of millions of Americans.

Chief Justice John G. Roberts Jr. sided with the majority in voting to uphold the law, Obama’s signature domestic initiative.

Passage of the legislation by the Democratic-controlled Congress in 2010 capped decades of efforts to implement a national program of health care. The legislation is expected to eventually extend health-care coverage to more than 30 million Americans who currently lack it.

Republicans in Congress and GOP presidential challenger Mitt Romney have vowed to try and repeal the measure after the November elections.

The health-care issue thrust the Supreme Court into the public spotlight unlike anything since its role in the 2000 presidential election. The court’s examination of the law received massive coverage — especially during three days of oral arguments in March — and its outcome remained Washington’s most closely guarded secret.

The court reviewed four questions: whether it was within Congress’s constitutional powers to impose an “individual mandate” to purchase health insurance; whether all or any additional parts of the law must be struck down if the mandate is rejected; whether an expansion of Medicaid was unduly coercive on the states and whether all of those questions can even be reviewed before the mandate takes effect.

On the Medicaid question, the judges found that the law’s expansion of Medicaid can move forward, but not its provision that threatens states with the loss of their existing Medicaid funding if the states declined to comply with the expansion. The finding immediately raises questions as to how effectively the federal government will be able to implement the expansion of the joint federal-state insurance program for the poor.

The most crucial issue before the court was considered to be the individual mandate, known technically as the “minimum coverage” provision, because striking it down would jeopardize the ability of insurers to comply with other, more popular elements of the health-care law without drastically raising premiums. Under those other provisions, for example, insurers can no longer limit or deny benefits to children because of a preexisting condition, and young adults to up age 26 are eligible for insurance coverage under their parents’ plans.

During oral arguments in March, conservative justices indicated they were skeptical about the individual mandate, the provision in the 2,700-page health-care law that requires nearly all Americans to obtain health insurance by 2014 or pay a financial penalty.

Arguing the case for the Obama administration, Solicitor General Donald B. Verrilli Jr. defended the law as a constitutional exercise of congressional power under the charter’s commerce clause to regulate interstate commerce. He said lawmakers were regulating health insurance to deal with the problem of millions of people who lack coverage and therefore shift costs to the insured when they cannot pay for their medical care.

The court rejected the commerce clause argument, but ruled that Congress nevertheless had the power to impose the mandate because it can be considered a tax.

Paul D. Clement, representing Florida and 25 other states objecting to the health-care law, argued that Congress exceeded its power in passing the law, which he said compels people to buy a product.

Although the most controversial provisions of the law are not scheduled to take effect until 2014, a complex web of new rules has already extended coverage and expanded benefits across the country.

No initiative has exemplified Obama’s progressive domestic agenda or inflamed his conservative opponents like the health-care law, officially called the Patient Protection and Affordable Care Act.

The court’s decision will resonate throughout the election season, not only in the presidential campaign but in House and Senate races across the country.

The law provoked an unlikely debate about the Constitution. Opponents saw it as a trespass on individual and state’s rights by an omnipotent federal government, and supporters viewed it as a long-sought guarantee of health care to Americans regardless of where they live or work.

As a mark of the case’s importance, the justices spent more than six hours over three days hearing oral arguments on the constitutional questions and related issues. It was the most time than the court has spent on any issue in nearly half a century.

As soon as Obama signed the health-care bill in March 2010, opponents raced to challenge it. Early court decisions followed a predictable pattern, with district judges appointed by Democratic presidents upholding the law and Republican appointees striking it down.

But at the appeals court level, that changed. In a decision by the U.S. Court of Appeals for the 11th Circuit in Atlanta, Judge Frank Hull, an appointee of President Bill Clinton, joined with a Republican colleague in saying that the individual insurance mandate in the “unprecedented” legislation exceeded congressional authority. The judges said that if the law were constitutional, it would be impossible to say what action on the part of the government would go too far.

At the U.S. Court of Appeals for the 6th Circuit in Cincinnati and the U.S. Court of Appeals for the D.C. Circuit, two prominent Republican-appointed judges agreed that the law is intrusive but said it is within Congress’s powers.

In Cincinnati, Judge Jeffrey Sutton, a George W. Bush appointee, was the deciding vote to uphold the act. In Washington, Senior Judge Laurence Silberman, named to the bench by President Ronald Reagan, wrote an opinion saying that the question was political, not constitutional.

“It certainly is an encroachment on individual liberty,” Silberman wrote. But then — alluding to other cases in which the Supreme Court has ruled that the commerce clause gives Congress power — he added that “it is no more so than a command that restaurants or hotels are obliged to serve all customers regardless of race, that gravely ill individuals cannot use a substance their doctors described as the only effective palliative for excruciating pain, or that a farmer cannot grow enough wheat to support his own family.”

Even as the legal wrangling grew to a crescendo, some aspects of the law were already being enforced. Those include requirements that many insurance plans allow young adults to stay on their parents’ policies until age 26; cover a range of preventive services, including birth control, without imposing co-payments or other out-of-pocket costs; eliminate lifetime dollar limits on coverage; and begin phasing out annual caps.

Also, can we talk about how Roberts swooped in with that swing vote and became all awesome? He is so gonna be hated by all the right wingers now. Love it.

And the initial gaff made by CNN and Fox, and how stubborn Fox was, was pretty hilarious.

Eh.

He has a legacy to protect. He was one of the most vetted and controversial selections -- and he's the figurehead of the sole branch government that needs to resolve conflict between the uberly inefficient Pres. and Congress. And, the Court has been so tainted since Bush/Gore, the Roberts/Alito/Sotomayor/Kagan confirmations, etc...seemed that there was an impetus to right the course.

Kennedy said the act was entirely invalid. We know he's the moderate, so it's difficult for me to buy that Roberts' decision wasn't strategic. Not that I don't think it's the right choice...and I'm certainly content!

I guess you could argue that upholding the rule was the "conservative" thing to do, even if it wasn't in line with his party, too.

Would love to get rid of Thomas on principle alone. Does he add anything?