WASHINGTON (AP) — The Supreme Court said Monday it will hear arguments next March over President Barack Obama’s health care overhaul — a case that could shake the political landscape as American are deciding if Obama deserves another term.

This decision to hear arguments in the spring sets up an election-year showdown over the White House’s main domestic policy achievement. And it allows plenty of time for a decision in late June, just over four months before Election Day.

The case could become the high court’s most significant and political ruling since its 5-4 decision in the Bush v. Gore case nearly 11 years ago effectively sealed George W. Bush’s 2000 presidential election victory.

The justices announced they will hear an extraordinary five-and-a-half hours of arguments from lawyers on the constitutionality of a provision at the heart of the law and three other related questions about the act. The central provision in question is the requirement that individuals buy health insurance starting in 2014 or pay a penalty.

In the modern era, the last time the court allotted anywhere near this much time for arguments was in 2003 for consideration of the McCain-Feingold campaign finance reform. That case consumed four hours of argument. This argument may spread over two days, as the justices rarely hear more than two or three hours a day.

The 2010 health care overhaul law aims to extend insurance coverage to more than 30 million Americans by requiring individuals to buy health insurance starting in 2014 or pay a penalty and other measures.

A White House spokesman said, “We are pleased that the court has agreed to hear this case.”

“We know the Affordable Care Act is constitutional and are confident the Supreme Court will agree,” communications direct Dan Pfeiffer said in a statement.

Senate Republican Leader Mitch McConnell called the law an “unprecedented and unconstitutional expansion of the federal government into the daily lives of every American.”

“In both public surveys and at the ballot box, Americans have rejected the law’s mandate that they must buy government-approved health insurance, and I hope the Supreme Court will do the same,” McConnell said.

Republicans have called the Patient Protection and Affordable Care Act unconstitutional since before Obama signed it into law in March 2010. But only one of the four federal appeals courts that have considered the health care overhaul has struck down even a part of the law.

The federal appeals court in Atlanta said Congress exceeded its power under the Constitution when it adopted the mandate. The federal appeals court in Cincinnati upheld the entire law, as did appellate judges in Washington, DC, in recent days.

In addition to deciding whether the law’s central mandate is constitutional, the justices will also determine whether the rest of the law can take effect even if that central mandate is held unconstitutional. The law’s opponents say the whole thing should fall if the individual mandate falls.

The administration counters that most of the law still could function, but says that requirements that insurers cover anyone and not set higher rates for people with pre-existing mediocal conditions are inextricably linked with the mandate and shouldn’t remain in place without it.

Lastly, the justices will consider whether arguments over the law’s validity are premature because a federal law generally prohibits challenges to taxes until the taxes are paid. The federal appeals court in Richmond, Virginia, ruled earlier this year reasoned that the penalty for not purchasing insurance will not be paid before federal income tax returns are due in April 2015, therefore it was too early for a court to make a ruling on the law.

The administration agreed to seek prompt Supreme Court review of the health care overhaul, though it had options for trying to delay the court’s consideration of the law until after the election. The Justice Department passed up the chance to ask the appeals court in Atlanta to reconsider its decision. It is common for the Justice Department to seek review by the full appeals court when a three-judge panel rules against the government.

Legal experts have offered a range of opinions about what the high court might do. Many prominent Supreme Court lawyers believe that the law will be upheld by a lopsided vote, with Republican and Democratic appointees ruling in its favor. Still others predict a close outcome, with Justice Anthony Kennedy, a Republican who sometimes joins his four Democratic colleagues, holding the deciding vote.

Six separate appeals have been filed with the high court. Three come from the Atlanta court, where the administration, the states and the National Federation of Independent Business appealed different aspects of the court ruling. From Richmond, Liberty University and Virginia appealed decisions turning back their challenges to the law. The Thomas More Law Center of Ann Arbor, Michigan, appealed a ruling by the Cincinnati-based court upholding the law.

Ultimately, the court chose the Atlanta court’s ruling as the primary case to review. That decision means that the highly regarded former Bush administration solicitor general, Paul Clement, is likely to argue on behalf of the challengers. The current solicitor general, Donald Verrilli Jr., is expected to defend the law before the justices.

Copyright 2011 The Associated Press.