Today the U.S. Supreme Court — without any dissent, even from the most conservative justices — refused to accept review of the Massachusetts decision requiring state officials there to recognize same-sex marriage. Although Supreme Court decisions in such certiorari proceedings are not precedential, it seems to me that this pretty much puts a nail into the coffin about whether the Court thinks the equal protection argument advanced in favor of gay marriage is invalid.
Just as the Court reached out in 2000 to decide Bush v. Gore, because it wanted to end the Florida recount, it could have done so with this case even though Massachusetts decided on state consitutional grounds. As the Court recognized in 2000:
The individual citizen has no federal constitutional right to vote for electors for the President of the United States unless and until the state legislature chooses a statewide election as the means to implement its power to appoint members of the Electoral College.
That same logic would obviously work to federalize same-sex marriage as a constitutional issue. But the Supremes said no, meaning there are still (believe it or not) some political questions in which the Court wants to avoid meddling. Glory be, a real conservative decision from a Supreme Court that is in actuality as activist as they come.