He wasn't "on the fence about it". He's just changed his position more often than some people change their tires.
Obama was for same-sex marriage in 1996, "undecided" in 1998, opposed in 2004 and 2008, and for it again in 2012.
Unambiguously.
Correct or not, that's irrelevant to the point I was making. The farthest he has ever gone against gay marriage is to say that he personally believed marriage was between a man and a woman. He never campaigned against it and even when personally opposed to it, consistently said that legislation like DOMA was unnecessary. That's hardly equivalent to giving $1000 to prop 8.