A poll  of former Supreme Court clerks found that 57 percent think the individual mandate will be overturned — up from 35 percent before the oral arguments. The InTrade political betting markets put the odds of an overturn at 76 percent. "The Supremes haven't handed down their ruling yet, and they could still surprise us," writes Kevin Drum. But:

If the court does overturn the mandate, it's going to be hard to know how to react. It's been more than 75 years since the Supreme Court overturned a piece of legislation as big as ACA, and I can't think of any example of the court overturning landmark legislation this big based on a principle as flimsy and manufactured as activity vs. inactivity. When the court overturned the NRA in 1935, it was a shock — but it was also a unanimous decision and, despite FDR's pique, not really a surprising ruling given existing precedent. Overturning ACA would be a whole different kind of game changer. It would mean that the Supreme Court had officially entered an era where they were frankly willing to overturn liberal legislation just because they don't like it. Pile that on top of Bush v. Gore and Citizens United and you have a Supreme Court that's pretty explicitly chosen up sides in American electoral politics. This would be, in no uncertain terms, no longer business as usual.

Legal academics are similarly concerned. While I was reporting out my New Yorker piece, I spoke with Akhil Reid Amar, a leading constitutional law scholar at Yale, who thinks that a 5-4 party-line vote against the mandate would be shattering to the court’s reputation for being above politics. “I’ve only mispredicted one big Supreme Court case in the last 20  years,” he told me. “That was Bush v. Gore. And I was able to internalize that by saying they only had a few minutes to think about it and they leapt to the wrong conclusion. If they decide this by 5-4, then yes, it’s disheartening to me, because my life was a fraud. Here I was, in my silly little office, thinking law mattered, and it really didn’t. What mattered was politics, money, party, and party loyalty.”

There's politics inside and outside the Court. (Melina Mara/The Washington Post)

And yet, would that really be so surprising? As an institution, the court is insulated from party politics, but the men and women who serve on it are increasingly selected through an intensely political process meant to insure that they don’t disappoint the party that promoted them. Both parties are trying to avoid nominating another David Souter, who had little paper trail and ended up disappointing his Republican sponsors by voting frequently with the court's liberals. One way parties find judges they can trust is to pick people who have served the party loyally in the past. Chief Justice John Roberts worked for President Ronald Reagan; Justice Elena Kagan worked for President Obama.

Similarly, the judges, who tend to live and work in Washington, are often ensconced in the social and professional networks of American politics. Justice Clarence Thomas’s wife, Ginny Thomas, has worked for Republican congressman Dick Armey, the conservative Heritage Foundation, and a Tea Party-affiliated group called Liberty Central, which has lobbied against the health-care law. If that's the group you hang out with on the weekends, how likely is it that you'll be able to give the Affordable Care Act a fair shake? Imagine what would happen to Thomas socially if he was the deciding vote to uphold the law.

The people who serve as judges on the Supreme Court have been vetted by political parties, have often worked for political parties, frequently have loyalties to people in political parties who helped their career, and spend much of their time in Washington, where they sort into social groups they find congenial. They are, in other words, more, not less, political than most Americans. So it would be very surprising if they were less, rather than more, polarized on an issue as politically polarizing as the health-care law.

Perhaps, as Drum says, the Supreme Court will surprise us on this one. But if they don't, I think the right question will be why so few in the legal academy saw it coming. If you think about the forces driving political polarization, and the process by which Supreme Court nominees are chosen, it's easy to see how it might take some time for the Court to become a truly polarized institution — lifetime appointments mean the composition of the court doesn't change very frequently — but it's almost impossible to see how it avoids becoming a polarized institution eventually. What we may be finding out is that "eventually" happened a couple of years ago.