Short answer: Almost nothing, but we’ve got 60+ hours to kill before the bomb drops so let’s get started on obsessively gaming this thing out.

First things first. There’s no guarantee that Roberts is writing for the Court, but because the justices tend to spread the opinion-writing duties around pretty evenly, it’s almost a lock that he’s the guy. According to Sean Trende, the only three members of the Court who haven’t yet written at least seven opinions this term are Sotomayor, Thomas, and the Chief. There’s no chance that Sotomayor is writing the majority opinion on O-Care; even if her side wins, the most senior justice in the majority gets to decide who writes the opinion. (The chief is considered most senior regardless of his actual tenure.) Roberts, Kennedy, Breyer, and Ginsburg are all senior to Sotomayor, so they’d all have to pass on an epochal opportunity to write the opinion for her to get it. Ain’t happening. There’s also virtually no chance that Thomas is writing the majority. He’s been on the Court for 20 years but he’s also relatively junior, trailing Roberts, Kennedy, and Scalia in tenure. And of course, he’s even more conservative than Scalia is, which makes him an unlikely pick to write a squishy opinion that’ll make Kennedy comfortable enough to win his vote. Long story short, Roberts is almost certainly handling this one. (Trende notes that Roberts didn’t write a single opinion in March or April, in fact. I wonder what his clerks were working on.)

Does that tell us anything about the majority on Thursday? Actually, yes: The long-feared scenario in which Kennedy joins with the liberals to form a 5-4 majority upholding ObamaCare is now impossible. Barring an almost unimaginable mindfark in which Roberts joins with the liberals to make it 5-4 while Kennedy votes with the conservatives, Roberts and Kennedy must be voting the same way. But … which way? Is it 5-4 to strike down the mandate (or the entire law) or is it 6-3 to uphold O-Care with Roberts and Kennedy joining the liberals? Your hunch on that depends on your impression of Roberts. I always assumed that, if this ended up as a 5-4 torpedoing of ObamaCare, Kennedy would be assigned the opinion because he is, after all, the swing vote and his reputation as a moderate who’ll side with the liberals in big cases would blunt some of the criticism afterward that this was a political vote. Maybe Roberts concluded that he can’t in good conscience fob this off on Kennedy; it’s his Court and this is the biggest decision it’ll ever make, so he’s going to man up and own it no matter how hysterical the cries of “politicization” are bound to be.

Or maybe he and Kennedy are voting with the liberals to uphold the law, either because they both agree with Breyer et al. on the merits or because Roberts is loath to see a case with this much political voltage end up in a 5-4 vote. There’s always a suspicion with chief justices that they worry a bit more about how the Court is perceived than the other members do; it’s the chief’s name that defines the era, after all, and it’s the chief who’s expected to build significant majorities in hot-button cases. (Earl Warren’s 9-0 decision in Brown v. Board of Education is the gold standard on that.) It may be that Roberts doesn’t want his era to be remembered for a galactically important Commerce Clause ruling decided by the narrowest, most contentious margin. Would he switch his vote to make it 6-3 if Kennedy was already determined to make it 5-4 to uphold? I don’t know. Mike Lee, his former law clerk, finds it hard to believe. Sean Trende, though, made an interesting observation on Twitter today: In the past, Scalia’s dissents in other cases have been grumpier than usual when he ended up losing on the big case of the term — not unlike today’s Arizona dissent, in fact. And that’s not just Trende saying that; that’s a former Scalia clerk whom Trende knows. (Guy Benson noted this also.) That’s weak, weak evidence of what Thursday will bring, but like I said, we’ve got 60 hours to kill. Weak evidence is better than none.

I said months ago that I thought we’d see a 6-3 vote to uphold. I’m less certain of that now but don’t think it’s nearly as unlikely as a lot of righty pundits seem to. It’s not hard to imagine a Roberts opinion larded up with lots of conservative-pleasing rhetoric about how mandates are unconstitutional generally but then ruling that they’re acceptable in the context of health care because of the unique nature of the market. (Kennedy seemed open to that logic at oral argument.) That’d be one way to split the baby; the other way would be if Roberts and Kennedy voted to strike down the mandate but preserve most of the rest of O-Care. That’s also distinctly possible, of course. It seems less likely to me that we’ll see anything more dramatic than that, like the entire statute being tossed. As I say, Roberts is going to fully own this now; that being so, nuking the Democrats’ signature legislative achievement in its entirety would be surprisingly bold.

Two parting thoughts. One: I predict we’ll see some sort of bogus rumor about a leaked decision circulating on Twitter or Drudge or somewhere in the next 48 hours. It won’t be true, but the anticipation’s so insanely high that some prankster won’t be able to resist. Two: We’ve been reading legal commentary on ObamaCare for two years and it occurred to me today that I don’t think I’ve seen a single analysis — not one — suggesting that one of the liberal justices might vote to strike this thing down. Granted, the balance of current Commerce Clause jurisprudence gives Congress expansive power in this area, but this is, after all, a case of first impression vis-a-vis the mandate — and yet, unless I’ve missed something, literally no one thinks any of the Court’s liberals might have qualms about taking this next step towards unchecked federal power over anything remotely commercial. Remember that on Thursday when you’re told that the Court’s conservatives are a bunch of politicized hacks.