I don't have much interest in speculation about the internal workings of the Supreme Court but not having seen much discussion of the unusual dissenting opinion by Justices Breyer and Kagan yesterday in the Hobby Lobby case, I thought I would speculate a bit myself about its significance.
The dissent is unusual for two reasons. First, it is jointly authored. Second, in contrast to Justice Ginsburg's dissent, Justices Breyer and Kagan refuse to decide the threshold question of whether Hobby Lobby and Conestoga Wood (as for-profit corporations) or their owners can bring claims under RFRA. Instead, they conclude that the claims brought in this case fail on the merits--and so they join only that portion of Justice Ginsburg's dissent. This is unusual, of course, because courts normally decide issues of standing (here statutory) before wading into the complexities of the merits of a case.
Two guesses about what was going on here.
The first guess is that Justices Breyer and Kagan have some sympathy to the possibility of RFRA claims brought by for-profit corporations. That would make seven justices (Justice Sotomayor joined Justice Ginsburg's dissent in full) at least open to such corporate RFRA claims. Why might Justices Breyer and Kagan be open to corporate RFRA claims? We should remember that Breyer was cozy with Ted Kennedy (RFRA's Senate shepherd) and Kagan worked in high-level positions under Bill Clinton (who signed RFRA into law). These connections might well have left both justices more sensitive to the goals of RFRA and wary about the future impact of Ginsburg's absolutist interpretation of the statute.
A second guess is that somewhere along the line Breyer and Kagan sought out a compromise position that would attract the vote of Justice Kennedy. Whether at conference or perhaps, Casey-style, when draft opinions were circulating they might have well suggested as an alternative approach what is reflected in their joint dissent: we'll leave open the door to RFRA claims by for-profit corporations but hold in a narrow opinion that under RFRA's balancing test the claims here fail. The problem, I'm guessing, is that Ginsburg--whose vote would be required to make a majority--refused to go along with that approach because she wanted to close the door entirely to the Hobby Lobbys of the world and so without her there was no chance of getting Kennedy either. Sotomayor either took the same hardline approach as Ginsburg from the outset (also dooming a majority around the Breyer-Kagan proposed compromise) or, if she was open to compromise, crossed over to Ginsburg's position (perhaps so Ginsburg didn't seem a lone voice) once it was clear a new coalition of five could not be formed.
Update: In response to my first guess, above, reader Adam White (whose own take on Hobby Lobby is here) writes helpfully to flag a 1999 e-mail (from the Clinton files) in which Elena Kagan described herself, among her White House colleagues, as "the biggest fan of RFRA (now RLPA) in this building."