US Supreme Court Justice Anthony Kennedy in Washington in 2007. Reuters/Kevin Lamarque The Supreme Court heard arguments Wednesday morning in a case that could gut Barack Obama's signature healthcare law, and legal experts are focusing on one comment from Justice Anthony Kennedy.

Kennedy, a key swing voter, said during the first half of oral arguments on Wednesday morning that he saw a "serious Constitutional" question with the interpretation of the Affordable Care Act (ACA) set forth by the plaintiffs who are trying to strike it down.

"If that's Kennedy's view of the case, there's almost no chance that the challengers can win," UCLA constitutional law professor Adam Winkler told Business Insider.

The fight over the ACA centers on whether the federal government can keep subsidizing insurance in the roughly three dozen states that have not set up their own insurance marketplaces. The health law laid out a plan in which states set up their own exchanges but said the federal government could step in and set up the exchanges for the states if they could not do it on their own.

In reality, 34 states have not set up their own exchanges. Opponents of Obamacare now say the law allows subsidies only in states in which a healthcare exchange has been "established by a state."

If the opponents win, people in those states would lose their health insurance unless the states set up their own exchanges. Kennedy appears to have a problem with that scenario because it would effectively coerce states into setting up their own exchanges if they wanted their citizens to have insurance. Kennedy doesn't like that because he is a big fan of federalism.

“There is a serious constitutional problem here if we adopt your position," Kennedy told the lawyer for the plaintiffs, according to The New York Times.

From SCOTUSBlog:

Simply put, Kennedy expressed deep concern with the federalism consequences of a reading that would coerce the states into setting up their own exchanges to avoid destroying a workable system of insurance in the state.

The high court will issue its opinion in the next few months, and all eyes will be on Kennedy and Chief Justice John Roberts, a conservative who surprised everybody in 2012 when he voted to save Obamacare.