Good try, but the right to marry is not mentioned in the Constitution, while the right to vote is. As far as I know SCOTUS has never overruled an actual vote of the people, and I know they have even thrown out challenges to marriage laws based on religious duty. This case should not be in court.
The US SC struck down a CO state constitutional AM, see; Romer v. Evans.
Prop 8 was filed in state court, but do to governmental plaintiff's, it was Petitioned to federal court and removal was granted.
In the 1st such case from CA in SF, 2004, the CA SC cited Baker v. Nelson, SCOTUS, as binding precedent, meaning they could NOT rule same sex marriage prohibitions violate the 14th AM.
This is why every state that permits them, does so under thier own Constitution.
I know GC does not agree with me on this point, but the CA SC itself ruled on the binding merits of Baker, not me.
You can bet your bottom $$ the ruling will cite Baker v. Nelson.
1. The court will rule the AM does NOT violate the 14th, per Baker.
2. The court will overrule Baker due to "doctrinal developments", such as Romer and Lawrence v. Texas. Baker was a summary decision, and the court explains that until the court releases inferior courts, only DD can do it, as I understood the CA SC 2004 ruling.
The FFC clause itself states Congress has the power to decide what records/acts must be given such FFC, hence DOMA.