We now know that the 4 conservative justices (including Kennedy) came down on the side of not just finding the mandate unconstitutional. They were in favor of striking the entire ACA. Almost no one predicted that as the final outcome because it would have been such an extreme position for the court to take. It would have forever tainted the "Roberts Court" as political and polarized.
So what were the Chief Justice's options? If the 4 conservative justices were as intransigent as their political counterparts, the only remaining choice he had was to work out a compromise with the 4 liberals.
Thinking about it that way takes me back to much of the conversation that was going on a couple of years ago about why President Obama nominated Elena Kagan. At the time, most people were talking about her potential to be an envoy to Justice Kennedy. But read this passage that was written back then and think about how it might apply to her working with Chief Justice Roberts on this decision.
Kagan distinguished herself as Dean of Harvard Law School by making peace between long-feuding factions on the right and the left. Few think she will be able to change the positions of the most devoted conservatives, Scalia, Roberts, Justice Samuel Alito and Justice Clarence Thomas. But apparently Obama thinks she may sway Kennedy...I doubt we're likely to learn about the machinations between Justices that went on behind closed doors unless one of them decides to write a particularly juicy memoir. But this seems like an extremely plausible scenario about how all this came down. If so, it would be fascinating that one of the first real breaks in the polarization President Obama has been fighting now for almost 4 years came - not in Congress - but in the Supreme Court.
But what's most important, her backers say, is her ability to work the process; her skill as a consensus builder, they argue, could eventually make a difference. Kennedy finds himself alone among the nine Justices on some issues, says Goldstein, and the question is which block of four can find the legal common ground to form a majority with him. "It's not infrequent that Kennedy is in a four-one-four posture and it's how you adapt to him that is what matters," Goldstein says. "It's not that she has intellectual capacities that others don't, but coalition building is a different thing, and she has an innate ability to find win-win solutions."