In effect, “leaving it to the states” is a tacit acknowledgement that gay marriage will become the law of the land — that it’s a fait accompli the minute a couple married in Massachusetts moves to Mississippi. Except rather than having a national discussion about it — rather than wrestling to find some coherent conservative solution (whether it’s that marriage is a special institution that should be between one man and one woman, or to support civil unions, or to say that marriage is a bourgeois institution with salutary benefits for everyone, including gays) — Republican politicians would be evading the issue.
For some, that’s a fine dénouement. In a sense, it’s Burkean. A slow, evolutionary implementation taking place over the course of decades (the courts would eventually mandate that Mississippi recognize Massachusetts’ marriage laws) would give society additional time to adapt to a changing world. That wouldn’t be the worst outcome — certainly better than a Supreme Court decision mandating the legalization of gay marriage everywhere immediately. (Though ironically, a court decision might be better politically for the GOP.)
But whether you’re for gay marriage or against it, let’s not pretend that advocating a patchwork of competing and disparate marriage laws is a profile in courage.