I voted for Romney, but I don't think that he would have been different. Basically, Romney is the father of homosexual "marriage" in America.
Also, this is a SCOTUS decision to Calfornia's state constitution. The federal executive branch has little to no influence on this decision.
I believe this administration is blackmailing members of Congress and the Supreme Court. That is how they are getting their votes and their rulings. With all his faults, I do not believe Romney would do that.