There’s a fair reason to think so and a not-so-fair reason. First, the not-so-fair:

Scalia’s dissent, at least on first quick perusal, reads like it was originally written as a majority opinion (in particular, he consistently refers to Justice Ginsburg’s opinion as “The Dissent”). Back in May, there were rumors floating around relevant legal circles that a key vote was taking place, and that Roberts was feeling tremendous pressure from unidentified circles to vote to uphold the mandate. Did Roberts originally vote to invalidate the mandate on commerce clause grounds, and to invalidate the Medicaid expansion, and then decide later to accept the tax argument and essentially rewrite the Medicaid expansion (which, as I noted, citing Jonathan Cohn, was the sleeper issue in this case) to preserve it?

Scroll down to page 138 of the justices’ opinions to see Ginsburg’s opinion described as a “dissent.” Minor problem with this theory: Her opinion was a dissent. She and the liberals lost on the Commerce Clause argument over the mandate, which is what the conservatives’ joint opinion was addressing when it referred to her view as dissenting. The terminology’s not inaccurate, just a little odd given that it was the conservative side that ultimately ate a big ol’ shinolaburger today.

Ed Whelan’s reason for thinking the conservative opinion was originally a majority opinion is more convincing:

The joint dissent issued by Justices Scalia, Kennedy, Thomas, and Alito certainly reads as though it were written to be the majority opinion. Among other things, the joint dissent’s discussion of the taxing power doesn’t respond to the Chief Justice’s opinion (indeed, I think it never even cites it). Rather, it addresses only the government’s argument. By contrast, the Chief’s opinion repeatedly takes issue with the joint dissent. This strongly suggests to me that the joint dissent was written first, as the proposed majority opinion, but failed to garner the fifth vote from the Chief…

One serious problem with the above theory is that it’s difficult to reconcile with the fact that the Chief would have assigned the majority opinion in the first place. An alternative theory is that the joint dissenters wrote their opinion as they did, after the Chief circulated his draft, in order to signal their deep dissatisfaction with his draft. I now lean towards this alternative theory.

I might have missed something but a quick skim through the conservative opinion has me thinking Whelan’s right: While they do address Ginsburg by name and answer her arguments directly, at no point do they address Roberts — even in the crucial section on the taxing power that ultimately upheld the mandate. (The opinion starts on page 127 in case you want to check our work.) Instead, their arguments are addressed to “the Government,” i.e. the DOJ and the Solicitor General. It strikes me as deeply odd that they wouldn’t tackle the chief head on when discussing the linchpin of the case given that it’s the main point of contention between him and them. And something else is strange too: The conservative opinion goes on to argue in methodical detail why the rest of the law shouldn’t be severable from the mandate. Quote:

The opinion now explains in Part V–C–1, infra, why the Act’s major provisions are not severable from the Mandate and Medicaid Expansion. It proceeds from the insurance regulations and taxes (C–1–a), to the reductions in reimbursements to hospitals and other Medicare reductions(C–1–b), the exchanges and their federal subsidies (C–1–c),and the employer responsibility assessment (C–1–d). Part V–C–2, infra, explains why the Act’s minor provisions also are not severable.

Major provisions of the Affordable Care Act—i.e., the insurance regulations and taxes, the reductions in federal reimbursements to hospitals and other Medicare spending reductions, the exchanges and their federal subsidies, and the employer responsibility assessment—cannot remain once the Individual Mandate and Medicaid Expansion are invalid.

Why would they bother with an intricate analysis of which provisions were severable from the mandate if this opinion was written in the knowledge that the mandate was ultimately being upheld? You only need step-by-step instructions on severability if you’re in the majority and obliged to provide lower courts with guidance on which parts of the statute are still operative and which aren’t. If you’re writing in dissent, that’s a waste of time. Which makes me think … maybe when this was written the author wasn’t in dissent.

So what happened here? Could be that this was written by the four conservative justices as a bizarro-world majority opinion as a sort of middle finger to Roberts on how things should have gone. But in that case, why didn’t they add language attacking his opinion on Congress’s taxing power specifically? It makes more sense to think this was the majority opinion at some point — perhaps written by Roberts himself (since he likely assigned the opinion to himself from the beginning) and then discarded after he switched his vote. The other conservatives then salvaged his opinion, polished it up a bit, and republished it as their own, possibly as a tacit rebuke to Roberts or possibly because Roberts switched so late in the game that there wasn’t time to draft something new from scratch. Or, as yet another alternative, maybe Roberts was on the fence all along, which spurred the conservative bloc and the liberal bloc to each write their own “majority” opinions in hopes of persuading him to join them as the fifth vote. When the conservative bloc ended up being disappointed, they left their opinion more or less as is, whether due to time constraints or pique or both.

Any other theories? I don’t buy the idea that Roberts flipped at the last minute because of all the liberal hacks screeching at him on MSNBC and in the New Republic. That was always a fait accompli. If he was going to vote to uphold for that reason, he would have been a solid yes from day one and the conservative opinion here would have looked very different. Exit quotation from Romney’s website: “As president, Mitt will nominate judges in the mold of Chief Justice Roberts and Justices Scalia, Thomas, and Alito.”