Statutory interpretation and textualism are important to conservatives like Roberts and Scalia, but that's never been Kennedy's wheelhouse. He's much more likely to make his mark on constitutional questions—and to consider broader issues, like the overarching purpose of a law, in statutory interpretation cases. He might be open to the Justice Department's argument that Congress intended for subsidies to be available in both state-run and federally run exchanges, irrespective of that "established by the State" language.
"His approach to text is maybe not as consistent as some of the other justices," Adler said.
The balance of state and federal power is also a pet issue of Kennedy's, and some of Obamacare's allies have played up a federalism argument in their briefs to the Court. A group of state governments, in an amicus brief in King, argued that a ruling invalidating the subsidies would upend the deal states thought they were making.
States always assumed that their residents would get subsidies no matter which level of government set up their exchanges, the states argue—some of them said so explicitly as they laid out their decision not to proceed on their own. If Congress meant to deny subsidies to residents of those states, it should have said so more clearly, they argue.
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"Congress did not give States clear notice that their citizens would be punished and their insurance markets ruined if the State chose [a federal exchange]," the states wrote.
Even lawyers on the other side of the case say that argument could work—maybe with Roberts, and more probably with Kennedy.
"My view on those is that they're serious arguments. They're intended to appeal to the chief and/or Justice Kennedy, I don't find them convincing under current precedent. "¦ [But] I think there are some justices on the Court who are open to moving the law in that direction," Adler said.
Not everyone is so sure Kennedy is up for grabs, though.
Some liberal advocates worry privately that he's simply too predisposed against Obamacare. And, while the Justice Department's brief—the one that counts—includes those federalism arguments, its primary emphasis is on the text and purpose of the statute, arguing that, read as a whole, the law clearly treats state and federal exchanges the same.
Harvard professor Lawrence Tribe, who recently published a book on the Roberts Court, believes Roberts might be open to that interpretation.
"A lot of conservatives say, 'The text is clear, it's about an 'exchange established by the state.' Roberts is not going to find it that simple. The text is at least ambiguous. It uses terms like 'such exchange' when referring interchangeably to an exchange that a state sets up itself and to the federal exchange a state might choose to treat as its own," Tribe told The Washington Post.
Roberts—not Kennedy—is probably the key to King, Tribe said in the same interview.
"I think it's very likely he will be. But it's possible that if he votes to uphold the administration's position, Justice Anthony Kennedy could conceivably join him," Tribe said. "But I think if he does not vote to uphold the administration's position, then it's almost inconceivable that it would be upheld."