The U.S. Supreme Court is set to begin hearing oral arguments Monday in a Republican-led challenge to the national health care law that has convulsed the country and its political class for more than two years — and may well define President Obama's tenure in the White House.

Call it what you will — the Affordable Care Act or Obamacare — the historic law and its insurance requirement signed by the president in March 2010 has spawned a hyperbolic vernacular (see: "death panels" and "Republicans want you to die"), multimillion-dollar special interest advertising campaigns and a slew of lawsuits with mixed outcomes.

It figured heavily in the Tea Party-fueled drubbing Democrats suffered in the 2010 mid-term elections when Republicans handily won control of the U.S. House. Obama described it as a "shellacking."

And it has emerged as an issue in the GOP presidential primary contests, where front-runner Mitt Romney has been forced to defend his embrace of a health insurance mandate when he was governor of Massachusetts.

The president's health care mandate, which was modeled on the Massachusetts plan? "Bad policy and wrong for America," Romney said Friday in a USA Today opinion piece.

The nine justices, who typically lean conservative 5-4, are expected to rule on the highly politicized case by June — right when Republicans wrap up their presidential primaries and caucuses.

Three Days Of Arguments

The court is scheduled to hear three days of arguments in the appeal filed by officials in 26 states — all but two led by Republican governors. They assert that the law's mandate that Americans buy health insurance is unconstitutional.

The 24 Republican governors, along with the GOP attorneys general in two states with Democratic governors, further argue that if the court kills the mandate, the entire law must die with it.

"You can't just carve it out of the bill," former Florida Attorney General Bill McCollum, who spearheaded the states' appeal, insisted recently. "It means the whole bill goes down."

That, in a nutshell, summarizes what's at stake in the case, one of the most politicized since the court decided Bush v. Gore in 2000.

Polls show that the country remains deeply divided on the law. A recent survey by the Pew Research Center found that 47 percent of those polled said they approve of the 2010 health care law, with 45 percent expressing disapproval. An ABC/Washington Post poll taken around the same time found 41 percent expressing support for the law, and 56 percent expressing disapproval.

How the question is framed does affect the outcome. The Pew question: "Do you approve or disapprove of the health care legislation passed by Barack Obama and Congress in 2010?"

The ABC/Washington Post question: "Overall, do you support or oppose the federal law making changes to the health care system?"

The Fifth Vote

In advance of the high court arguments, politicos and court-watchers have been consumed not only by the merits of the case, but also by how public opinion and party pressure may influence a court that has come under increased scrutiny for perceived political bias.

And speculation is rampant about how far — or not — the court might go when it rules on Obama's premier domestic victory. Judicial activism? Judicial restraint? Precedent or political push-back?

"I don't think [Chief Justice] John Roberts wants to be the fifth one if there are only five votes to strike down the mandate," Supreme Court expert Lyle Denniston of SCOTUSblog said during a recent briefing on the case. "If there are six votes and the sixth vote to strike down the mandate is from John Roberts, [he'll] go along with that rather than have the court do it by a five-vote majority."

"I don't think John wants to have the decision that close," Denniston said.

Lawyers, journalists and academics who follow the Supreme Court appear to agree. A recent survey by the American Bar Association found that 85 percent of court experts polled said they believed that a majority of the justices will find the insurance mandate constitutional.

A Penalty Or A Tax?

The court may not even get to a point where justices, in their deliberations, will consider the mandate issue.

On Monday, the first issue addressed by the court will be the question of whether it has the right, or jurisdiction, to hear the case. There will be lots of discussion about the obscure-sounding federal Anti-Injunction Act.

The AIA prevents federal courts from "hearing cases where taxpayers are seeking court orders, such as injunctions, to prevent the government from assessing or collecting federal taxes."

The health care law will by 2014 impose a monetary penalty on individuals who fail to buy insurance. The argument on jurisdiction will hinge on whether the penalty, collected "in the same manner as taxes," according to the law, is a "penalty" or a "tax."

If the AIA does apply, write law professors Bryan Camp of Texas Tech School of Law and Jordan Barry of the University of San Diego School of Law, "courts likely will not be able to decide whether the Affordable Care Act is constitutional until at least 2015." That's because the law won't take effect until 2014, so no one will pay the tax — and have the standing to bring suit — until the following year.

If the court decides that, under the AIA, it does not have a right to hear the states' suit, it would invalidate court rulings on the constitutionality of the health care law thus far, the professors write in a previous assessment of the case. Except, experts note, for one case out of the 4th Circuit, which ruled that the AIA says the federal court has no jurisdiction in the case.

Medicaid Expansion

The justices on Wednesday will also hear arguments about the health care law's expansion of Medicaid to a much wider swath of poor Americans.

This is a break-the-bank issue for states, McCollum argues, broadening those covered and requiring the medical personnel to handle the new recipients.

But law advocates, like Simon Lazarus of the National Senior Citizens Law Center, argue that if the court invalidates the expansion, it could serve to undermine other federal aid programs.

While the court will consider issues of its jurisdiction over the case and hear arguments about Medicaid expansion, the heart of the case remains the individual mandate and its role in attempting to fix what all sides agree on: a broken health care system.

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