WASHINGTON » The weight of a Supreme Court decision isn’t likely to settle the contentious debate over health care in America, a nation disdainful of big government and historically unable to guarantee affordable basic coverage to all its citizens.

The court announced Monday it will take up the constitutional challenge to President Barack Obama’s landmark health care law, with a decision expected next summer in the thick of the presidential election. But even if the law is upheld, Republican congressional leaders say they’ll keep crusading for its repeal.

Administration officials respond with a dose of hope and bravado. Publicly, they’re confident Obama’s plan for covering the uninsured will be upheld to the last comma.

But privately, there’s a Plan B: If the court strikes down the law’s unpopular linchpin — the so-called individual mandate requiring most Americans to carry health insurance — the administration would take whatever’s left and try to put that into in place.

"Either way it rules, the Supreme Court decision will not end the debate on health care," said former Senate Majority Leader Tom Daschle, an influential Democratic adviser. "It is, and will largely remain, a debate on the role of government."

That’s pretty much how Republican congressional leaders see it, too.

"Job-killing tax hikes on families and small businesses may well be constitutional — that doesn’t mean we would support them," said Senate Republican Leader Mitch McConnell of Kentucky.

House Speaker John Boehner of Ohio remains committed to repealing the overhaul and replacing it with a Republican plan regardless of the Supreme Court ruling, his spokesman said.

The law’s coverage expansion to more than 30 million uninsured is still two years away, but the Supreme Court took the case after lower courts split and the administration, as well as its opponents, asked for a decisive ruling.

Of four federal appeals courts that have ruled, two upheld the law, one struck down only the insurance mandate, and one punted, saying it is premature to decide the merits until the law’s main coverage provisions take effect in 2014.

Appeals courts in the District of Columbia and Cincinnati that upheld the law found that requiring Americans to carry health insurance — even if intrusive — is within the power of Congress to regulate interstate commerce.

Starting with 2014 tax returns, the law imposes a penalty on those who do not have coverage through an employer or a government program, or through individual purchase. In passing that requirement, a Democratic-led Congress found that the health care system is a major part of the national economy and that insurance can’t work if people can postpone getting coverage until they become sick.

A federal appeals court in Atlanta saw things differently.

Ruling against the administration in a lawsuit by 26 states, that court found that Congress overstepped its constitutional authority by imposing the insurance mandate. The unprecedented requirement to carry health insurance would force average citizens to buy an expensive product from a private company from cradle to grave, the majority said.

While the biggest controversy is over the mandate, the law has other major provisions.

To make it affordable for the uninsured to obtain coverage, Congress expanded the Medicaid program for low-income people and set up a system of tax credits for middle-class people who purchase their own policies. It also barred insurers from turning away those in poor health or charging them more.

The Supreme Court’s decision will turn on legal precedents developed through the decades, as the federal government sought to extend its reach over economic affairs. But the immediate impact of a decision in 2012 is likely to be political.

Upholding the law will be seen as vindication for Obama’s approach to governing, said Robert Blendon, a Harvard public health professor who follows opinion trends on health care. "This is not only an issue of whether or not the bill is constitutional, or what is the best public policy," said Blendon. "It’s an issue about the judgment of the president."

At the other end of the spectrum, the Supreme Court could strike down the entire law, validation for Republicans who from the start called it government overreach. But no appeals court has gone that far.

A mixed verdict would create its own problems. The court could strike down only the insurance mandate, leaving the rest of the law in place. That includes a Medicaid expansion expected to help about 16 million uninsured people, the creation of new state health insurance markets, Medicare cuts and a slew of regulations.

While the Obama administration would still be left with pieces of a law to carry out, the demise of the insurance requirement would create a real crisis for the insurance industry. Insurers may be forced to accept patients who apply after getting sick, but at the same time deprived of a larger pool of insured people over which to spread their costs.

Administration lawyers maintain that if the insurance mandate is struck down, the requirement that insurers accept people in poor health should also be invalidated. But the justices don’t have to follow that advice.

Sooner or later, the whole muddle could wind up back in Congress.