“He’s very clear about the fact that his position is evolving.”

That’s from White House press secretary Jay Carney, describing Obama’s position on gay marriage at the press briefing today. I think this should go down as a key moment, one that demonstrated as clearly as you could want that Obama’s current position on gay marriage is untenable.

Ben Smith has the video:

The whole exchange is worth watching. The trouble started when Carney was asked whether Obama’s signature on a 1996 questionnaire indicating support for gay marriage meant that Obama did, in fact, support gay marriage at the time. Carney said:

What I know is what his position was during the campaign and what it is now. He’s been very clear about it. He was very clear in the campaign. He’s very clear about the fact that his position is evolving. I don’t have anything to add to that.

This is going to irk gay advocates in a big way. Obama first declared that his position on gay marriage is evolving back in October, when he told gay advocates that he is wrestling with the issue, and that “attitudes evolve, including mine.”

That was nearly eight months ago. While it’s undoubtedly true that the arc of history bends towards justice slowly, as Obama himself is fond of saying, they will naturally ask how much longer it will take until his position completes its evolution.

Obama is set to attend a gay-themed fundraiser later this week in New York, a state where gay marriage is close to becoming legal, and he is certain to be pressed to clarify where his position now stands. He will be expected to give a better answer than his current one.

Today’s White House “claim that Obama has been clear that his position is evolving highlights the fundamental untenability of this position. To be clear, Carney is in a very tough spot. This isn’t an easy position to sell or explain. And it’s absolutely true, as Carney says, that Obama has a strong record on gay rights. He deserves enormous credit for helping to create the political conditions necessary to ensure that don’t ask don’t tell got repealed. He declared that his administration would stop defending the Defense of Marriage Act in court — not a politically easy thing to do by any means.

But the basic problem here is this: As much credit as Obama deserves for these actions, they further highlight what everyone already knows — that Obama fundamentally believes in full equality for gays and lesbians. This circle won’t be closed until Obama takes the final step of supporting marriage equality. Everyone knows full well where this story will end. Multiple national polls show that for the first time, majorities now think it should be legal for consenting gay adults to marry and enjoy the benefits of marriage.

It seems obvious that Obama, too, believes this, and that he will even say so out loud soon enough.