I wondered about this on the afternoon of the decision. It stands to reason: If, as most everyone believes, Roberts initially assigned the majority opinion to himself and then ended up flipping at the eleventh hour, the four conservative dissenters would have had to scramble to come up with an opinion of their own while handling the rest of their caseload. (Roberts authored no other opinions over the final two months of the term so he and his clerks could conceivably have drafted something new from scratch late in the process.) The easiest way to do that would be to salvage Roberts’s orphaned majority opinion — or, at least, the bits he wasn’t keeping for himself — and re-work as necessary. Maybe they took the sections he discarded on the tax power and severability, tacked on their own section rejecting the Commerce Clause argument, and called that a dissent. Using Roberts’s own words against him would have been a pointed rebuke to him for flipping, even if the Court and its clerks are the only ones with enough background on this process to fully appreciate it.

My source insists that “most of the material in the first three quarters of the joint dissent was drafted in Chief Justice Roberts’ chambers in April and May.” Only the last portion of what eventually became the joint dissent was drafted without any participation by the chief justice.

This source insists that the claim [in Jan Crawford’s CBS story] that the joint dissent was drafted from scratch in June is flatly untrue. Furthermore, the source characterizes claims by Crawford’s sources that “the fact that the joint dissent doesn’t mention [sic] Roberts’ majority … was a signal the conservatives no longer wished to engage in debate with him” as “pure propagandistic spin,” meant to explain away the awkward fact that while the first 46 pages of the joint dissent never even mention Roberts’ opinion for the court (this is surely the first time in the court’s history that a dissent has gone on for 13,000 words before getting around to mentioning that it is, in fact, dissenting), the last 19 pages do so repeatedly.

That’s lefty law prof Paul Campos writing for lefty web zine Salon. Did a mischievous liberal clerk leak to them in order to embarrass the conservative dissenters? Could be, except that … this is more embarrassing to Roberts than to Scalia and company. The idea that his words are on both sides of the Court’s decision makes the outcome seem that much more bizarre and his supposedly principled change of heart seem that much more dubious. He’s talking, almost literally, out of both sides of his mouth. It’s a shot at his credibility and the Court’s institutional legitimacy, which was supposedly the basis for his decision, more than it is a shot at the conservative dissenters. Why would a liberal clerk want to sandbag him for siding with them on the biggest case they’ll ever rule on?

Then again, if this is true, why wouldn’t the (presumably conservative) Court sources who leaked to Jan Crawford have simply said so? Obviously, they didn’t borrow his discarded opinion because they’re lazy. They borrowed it because they were pressed for time and/or because they wanted to make a point — or, just maybe, because they held out hope to the bitter end that he’d switch back and join them in striking down the law. By keeping the dissent intact as a potential majority opinion rather than larding it up with language lashing out at Roberts, the four conservatives made it as easy as possible for him to reconsider and climb back aboard right down to the wire. To my mind, that’s the best explanation for the tone of the opinion, the inclusion of the otherwise gratuitous severability section, and the lack of any references to Roberts’s opinion. They weren’t working on a dissent, they were working on a shadow majority, ready to go right out of the box in case Roberts came back into the fold. (Crawford notes that Kennedy was lobbying Roberts up to the last minute, in fact.) That doesn’t settle the issue of who authored most of the eventual dissent — maybe it was mostly Roberts’s draft or maybe it really was co-drafted by Scalia, Kennedy, Thomas, and Alito with an eye to winning Roberts back over — but it settles most everything else.

Here’s Krauthammer accusing Roberts of letting the left intimidate him. Exit question via TNR: Were Thomas and Kennedy the CBS leakers?