Rep. Barney Frank said yesterday that Obama would stop defending DADT in court if repeal was defeated:

Yes, he will drop his defense of it because the argument has been, ‘well you’re the president and you have this obligation,’ and I think that’s generally right. We don’t the president picking and choosing what laws they defend in court. But this one will have lost its legitimacy, it’s moral legitimacy, it’s majoritarian claim. It won’t be a case anyone could argue in the courts – overturning the will of the voting public.

Things are looking optimistic for repeal right now, otherwise this statement would be a very big deal. Hopefully we’ll never have to find out if it’s actually true.