Obama has said his position on Marriage Equality has been evolving, probably not. Public opinion however, has been evolving, as have the demographics. The old, rigid, fearful of gays, generation of voters has been dying off.
They’re being replaced by a generation that began voting right after Y2K. Remember the computer panic by that name? It was a real threat, and not just a hoax, but not the end of the world the way the same people who have lately been selling gold made it out to be. (BTW, gold dropped under $1600/oz today, it could be on the way down to $700)