Most conservative constitutional scholars have even written that they cannot see how it passes Constitutional muster if it reaches the Supreme Court, which is why the fight has been to try to keep the Supreme Court from addressing the issue.
Bush tried to pre-empt a Supreme Court decision through a Constitutional Amendment, however, it never gained enough support to go anywhere.
The reality is, the only way that gay marriage is going to be stopped in the United States is if there is a Constitutional Amendment that prevents it.
I expect the SCOTUS to strike down Prop-8 eventually as unconstitutional and the battle will be whether this country wants to pass a Constitutional Amendment that for the first time in the history of this country, takes away rights rather than expands them.
That is where the true battle is going to be on this issue.