Well, he is a politician. I doubt he could say that he fully supports gay marriage 100% even if he did. Political consultants probably won't let him. Or any other candidate for that matter.
I think Obama might be our best chance. At least he's talking about something of a step forward, rather than the other direction. Obviously, what he's talking about is not ideal, but I guess I'm enough of a pessimist that I'm not surprised, or even much upset by it.
I realize that politics is a pretty volatile topic, and might wind up starting a bit of a flamewar (not my intention). So, with that in mind:
My opinion about politics is that everyone makes a lot of great talk, but what we're ultimately talking about when passing laws is trying to get 100 Senators and something like 300+ Representatives to agree on something. Not going to happen. Why do you think Bush was unable to pass the abortion bans he wanted to even when the Republicans had control of Congress? Or any of the other social conservative agenda he got elected with? There were still enough Dems left to stop him. Simple as that.
Instead of doing something good for the US, he wasted all his political capital on a social agenda that didn't have a snowball's chance in hell of making it out of even one house (I'm thinking all the stuff that got him elected-- let's have prayer in schools, a constitutional amendment protecting the institution of marriage, ban on all abortions, not just "partial birth"). Yeah, he got the DOMA but that's not an earth shattering victory considering the bulls%^$ he was shoveling during his campaign.
Anyway, I think it'll work the other way if Obama or Clinton gets the Presidency and Dems retain control of Congress. There will still be enough Republicans left to stop full equality for LGBT people. I think that what Obama is talking about is at least feasible rather than just a pipe dream.
Don't even get me started on the Supreme Court....