I outline some reasons to be skeptical about whether Kennedy would be willing to cast a fifth vote to hold bans on same-sex marriage unconstitutional here. At a minimum, there’s no reason to simply assume that “[t]here are 5 votes for a constitutional right to same-sex marriage.” The typically overrated assertions of America’s most overrated justice notwithstanding, it wouldn’t be remotely difficult for Kennedy to distinguish Lawrence and Perry if he wanted to do so. It might be different if Lawrence had been based on equal protection, but the fact that it was a privacy case gives him an easy exit route. All he would have to do is point to the status quo on abortion, in which the state cannot ban abortion but can exclude abortion from medical funding, although the central purpose of the Hyde Amendment is to obstruct the exercise of a constitutional right. And there are other important contextual differences between this case and the major liberal (or half-liberal) rulings Kennedy has joined: upholding Perry would have a much larger policy impact and have significantly less public support. It’s possible that Kennedy could provide a fifth vote to uphold Perry, and it was shrewd of Walker to cite Kennedy as much as he could, but on the basis of what we know I would definitely bet against it.
One thing I didn’t address is the possibility that there could be some way of upholding Prop 8 without creating a national right to same-sex marriage (in a manner similar to the way Romer ruled Colorado’s Amendment 2 unconstitutional without explicitly overruling Bowers.) I’m very skeptical about this, in part because it’s hard to see any way of invalidating Prop 8 that wouldn’t apply to other same-sex marriage bans (whether or not the Court makes that explicit.) One intriguing possibility suggested by a commenter is that Prop 8 could be considered irrational because California already grants all of the material benefits of marriage, so refusing to apply the title of marriage to same-sex unions is just raw discrimination that the Court ruled unconstitutional in Romer. I don’t know if Kennedy would buy it, but it’s a clever argument. But the problem is that — like conservative attempts to have the insurance mandate ruled unconstitutional — it would be very much a “be careful what you wish for” outcome. Because it would create a perverse incentive for states that don’t want to recognize same-sex marriage rights to keep their marriage regimes as inequitable as possible in order to avoid a challenge under Perry/Schwarzenegger, it would probably make the policy status quo worse in the short term. It’s possible that Kennedy (or even Roberts) could write such an opinion, but I wouldn’t count that as a victory for same-sex marriage rights, although at least it would make future challenges to marriage discrimination easier to mount.