WASHINGTON — The Supreme Court has set aside an entire week in March to hear arguments over the constitutionality of President Obama’s health care overhaul.

All told, the court will hear five hours of arguments over health care reform. Legal historians note that devoting that much time to the arguments in a case is unprecedented in the history of the Supreme Court.

In the modern era the last time the court devoted approximately that much time to arguments in a case was in 2003 for consideration of the McCain-Feingold campaign finance overhaul. That case consumed four hours of argument.

Arguments over whether the health care reform law — formally known as the Patient Protection and Affordable Care Act — violates portions of the Constitution will be heard March 26 through March 28. The arguments fill the entire court calendar that week.

Court watchers say the justices’ ruling — expected before Independence Day — will have implications for the 2012 presidential election. A ruling this summer will come in the middle of the presidential election campaign and, depending on which way it goes, it could sway undecided voters one way or another.

All of the president’s prospective Republican challengers have opposed the bill, and many opponents of the reforms have branded the law unconstitutional since before Obama signed it in March 2010. At the heart of the opposition to the law is the so-called individual mandate, which requires every American to obtain health insurance in 2014 or pay a penalty.

The Supreme Court will start the week of arguments on March 26 with one hour on whether court action is premature because no one yet has paid a fine for not participating in the overhaul. Federal law generally prohibits challenges to taxes until they are paid, and the 4th U.S. Circuit Court of Appeals in Richmond, Va. ruled last year that the penalty for not purchasing insurance will not be paid before federal income tax returns are due in April 2015, therefore it is too early for a court ruling.

Arguments on Tuesday, March 27, will take two hours, with lawyers debating the central issue of whether Congress overstepped its authority by requiring Americans to purchase health insurance.

The White House has defended the individual mandate by noting that Congress used a “quintessential” power — its constitutional ability to regulate interstate commerce, including the health care industry — when it passed the overhaul. But opponents of the law, backed by a ruling last year by the 11th U.S. Circuit Court of Appeals in Atlanta, say that Congress overstepped its authority when it passed the individual mandate.

A divided Atlanta court panel ruled that Congress cannot require people to “enter into contracts with private insurance companies for the purchase of an expensive product from the time they are born until the time they die.” The Atlanta court is the only one of four appellate courts that found the mandate to be ­unconstitutional.

The final day’s arguments — on Wednesday, March 28 — will be split into two parts, with justices hearing 90 minutes of debate over whether the rest of the law can take effect even if the health insurance mandate is unconstitutional and an extra hour of arguments over whether the law goes too far in coercing states to participate in the health care overhaul by threatening to cut off federal money.

Opponents of the law say the whole package should be tossed out if the individual mandate falls. However, the administration has been adamant that most of the law still could function but that the requirements that insurers cover anyone and not set higher rates for people with preexisting conditions are inextricably linked with the mandate and shouldn’t remain in place without it.

Besides hearing arguments over the constitutionality of the health care reform law, the Court will look at the expansion of the federal-state Medicaid program that provides health care to poorer Americans even though no lower court called that provision into question.

Florida and 25 other states argued unsuccessfully in lower courts that the law goes too far in coercing them to participate by threatening a cutoff of federal money. The states contend that the vast Medicaid expansion and the requirement that employers offer health insurance violate the Constitution.