Provided that Civil Unions with the same rights are created. He is on record as saying that Civil Unions are a necessary requirement of his support for the marriage ban.
As Homebrew pointed out, this grossly misstates his position. He was willing to trade prohibition of SSM for full civil unions as a compromise: given that the alternative seems to be eliminating SSM without any civil unions.
I was just reading about this today in the New York Observer (great weekly paper, btw). I think the statistic was that 66% of those under 30 support SSM, and that 73% of those over 50 are against it. Something like that, but it definately showed that the people who have the problem with it are the older generation.
And since older people vote in higher numbers than younger people, well, the youngums will have to wait a while longer.