The jurisdictional arguments were even more complicated today, but if the Supreme Court reaches the merits, there seem to be five votes to strike down DOMA’s Section 3: the four “liberal” justices on equal protection grounds and Justice Kennedy because the federal government is intruding on state authority to regulate marriage. Now, my prediction is worth what you paid for it – and one or more of the liberals (or even Chief Justice Roberts) could join Kennedy to make the resulting ruling less stark — but there are good reasons to believe that a 4–1‑4 merits decision is possible even if Kennedy is ultimately persuaded by the equal protection claim. To the extent the swing justice is wary of the political implications of striking down all states’ marriage laws, then he might not want a ruling that would set the logical precedent for such a move. There was a definite sense at the Court that the provision of DOMA that limits marriage to opposite-sex couples for purposes of federal law isn’t long for the world, but a 4–1‑4 decision would have no controlling theory.

More broadly, on a day when oral argument got surprisingly more lively than it did over California’s Prop 8 yesterday, all the justices took the opportunity to ask pointed questions of the various counsel arguing issues that ranged from the U.S. government’s awkward participation in the case, the standing of the House of Representatives to defend DOMA, the meaning of equal protection, and the role of federalism in all this. Justice Kagan focused on the “moral disapproval” that motivated Congress to pass DOMA in 1996, Chief Justice Roberts expressed growing frustration with Solicitor General Verrilli’s treatment of federal-state relations, and Justice Kennedy continued musing aloud about whether and how to decide the case. We’re in for a real cliffhanger of a ruling.