In the WSJ. Favorite passage:

[B]asic constitutional rights cannot depend on the willingness of the electorate in any given state to end discrimination. If we were prepared to consign minority rights to a majority vote, there would be no need for a constitution.

This is absolutely right, and a much overlooked — albeit rather basic — point.  While it is nice if majorities in states vote for marriage equality, it is rather irrelevant.  As a matter of constitutional principle, we don't submit questions of equal treatment under the law to majority vote.  Those rights are already constitutionally guaranteed to all citizens.

A bit more:

The Supreme Court has repeatedly held that the right to marry the person you love is so fundamental that states cannot abridge it. In 1978 the Court (8 to 1, Zablocki v. Redhail) overturned as unconstitutional a Wisconsin law preventing child-support scofflaws from getting married. The Court emphasized, “decisions of this Court confirm that the right to marry is of fundamental importance for all individuals.” In 1987 the Supreme Court unanimously struck down as unconstitutional a Missouri law preventing imprisoned felons from marrying.

There were legitimate state policies that supported the Wisconsin and Missouri restrictions held unconstitutional. By contrast, there is no legitimate state policy underlying Proposition 8. The occasional suggestion that marriages between people of different sexes may somehow be threatened by marriages of people of the same sex does not withstand discussion…. Moreover, there is no longer any credible contention that depriving gays and lesbians of basic rights will cause them to change their sexual orientation. Even if there was, the attempt would be constitutionally defective. But, in fact, the sexual orientation of gays and lesbians is as much a God-given characteristic as the color of their skin or the sexual orientation of their straight brothers and sisters. It is also a condition that, like race, has historically been subject to abusive and often violent discrimination. It is precisely where a minority’s basic human rights are abridged that our Constitution’s promise of due process and equal protection is most vital.