On Thursday morning, nine U.S Supreme Court justices will rule on Florida vs. the Department of Health and Human Services, a seemingly innocuous case to the casual observer that nevertheless could have a profound impact on the future political fortunes of Barack Obama and his legacy.

The highly anticipated ruling will delve into the constitutionality of the Patient Protection and Affordable Care Act, Obama's controversial health-care law, derisively referred to by its Republican critics as Obamacare, and considered to be the U.S. president's signature domestic policy achievement.

How the court will rule has become great fodder for and speculation among political observers. But many believe the court will, as it usually does on big decisions, split along ideological lines — conservative-leaning judges ruling to scrap all, or parts of the law, and liberal-leaning judges arguing the law should be upheld.

This means it could all come down to Justice Anthony Kennedy, considered the swing vote on the court, and as conservative columnist Charles Krauthammer joked, “whatever side of the bed [he] gets out of that morning.”

The law seeks to cut skyrocketing health-care costs and extend health insurance to 30 million uninsured Americans. But the most contentious issue and core provision of the act is the so-called individual mandate, which forces Americans to purchase health insurance under threat of a financial penalty.

Part of the Supreme Court ruling then will focus on, and could define for generations, the power of one section of the constitution known as the commerce clause, which states that the U.S. Congress has the power “to regulate commerce …among the several states."

Commerce clause

It’s this clause, the Obama administration asserts, that gives the federal government the right to legislate Americans into purchasing health insurance, whether they want it or not.

But this has been challenged by officials in 26 states, led by Florida, who argue the White House is overreaching in its interpretation of the clause. They claim the federal government has no right to compel private citizens to purchase a certain product, in this case health insurance, that the law infringes on state rights, and that the individual mandate should be struck down as unconstitutional.

President Barack Obama has staked much of his political capital on the health-care law. (Carolyn Kaster/Associated Press)

Obama, who has staked much of his political capital on the law, has not budged on the issue. In April, he warned that the Supreme Court would be taking an "an unprecedented, extraordinary step" if it struck down the legislation passed by the country's elected representatives. (As the court often overturns laws, the president later clarified his remarks, saying he was referring to rulings on economic issues).

He also turned the issue around on the Republicans, hinting there is GOP hypocrisy since they have for years decried "judicial activism" of courts and lack of judicial restraint.

Still, some Democrats, who initially seemed confident the law would hold up constitutionally, have begun to grow concerned over whether the court will rule in their favour.

There was also little comfort provided by what many feel was the sub-par performance of White House lawyer U.S. Solicitor General Donald Verrilli during oral arguments. Adam Serwer of the left-leaning Mother Jones proclaimed that it “may go down as one of the most spectacular flameouts in the history of the court.”

It's difficult to determine with any certainty how the justices will rule based on their questions during those arguments. Conservative justices zeroed in on the logical implications of allowing the mandate to stand.

Forced to buy broccoli?

Supreme Court Justice Antonin Scalia suggested that if the government has the power to mandate health insurance, it would mean federal lawmakers could also compel its citizenry to buy broccoli.

"Could you define the market — everybody has to buy food sooner or later, so you define the market as food, therefore, everybody is in the market; therefore, you can make people buy broccoli," he said.

But liberal Justice Ruth Bader Ginsburg seemed to defend the mandate, saying that those who choose not to have health insurance make it more expensive for anyone else.

“It's not your free choice just to do something for yourself. What you do is going to affect others, affect them in a major way,” she said.

Justice Sonia Sotomayor also hinted support for the mandate, adding "there is government compulsion in almost every economic decision because the government regulates so much."

The decision could come down to Justice Anthony Kennedy, considered the swing vote on the court. (Damian Dovarganes/Associated Press)

All eyes then were on Kennedy who seemed to follow the conservative-line of questioning. He asked whether the government has "a heavy burden of justification to show authority under the constitution" for the mandate and that it "threatens to change the relationship between the government and the individual in a profound way."

While the court could rule to scrap the individual mandate, other parts of the bill could be upheld.

Americans opposed to mandate

Indeed, polls show that while the majority of Americans are opposed to "Obamacare" as a whole, and in particular, the individual mandate, they support many provisions of the bill, which include forcing insurance companies to insure those with pre-existing conditions and that individuals can stay on their parents' health-care coverage until they are the age of 26.

Yet many have suggested that without the individual mandate centrepiece, the whole bill could fall apart.

The political ramifications can only be surmised but some Democrats have complained the issue has already cost the party. Many blame the unpopularity of the bill for their loss of six seats in the Senate and control of the House in the midterm elections.

Some Democrats have already suggested that pushing the health-care issue forward was political capital wasted, when resources should have been focused on helping aid the economy — the No. 1 issue with voters.

But Democratic strategist James Carville recently opined that striking down the law would be the best thing for the party because health-care costs will escalate.

"You know what the Democrats are going to say — and it is completely justified: ‘We tried, we did something, go see a 5-4 Supreme Court majority,’” Carville told CNN.

"There’s nothing better to me than overturning this thing 5-4 and then the Republican Party will own the health-care system for the foreseeable future."

With files from The Associated Press