You dork. You numb-skulled fondler of inappropriate species.
It's a really basic skill. If you need to, hire someone to follow around behind you to shout "IT'S A TRAP!"...
The whole same sex marriage thing? You really should have just kept your mouth shut, because the issue costs you votes either way.
You come out supportive of same sex marriage? You end up pissing off the theocratic bigots amongst your base, and you need their votes no matter how loathsome they may be. You come out opposed to same sex marriage? You confirm the fears of any fence-sitters, you hand Obama a stick to beat you with, AND you peeve the younger voting demographic that's more libertarian in orientation (and thus largely favors same sex marriage) all in one fell swoop.
Shutting the hell up is the indicated alternative. A good second best is pointing out that marriage is simply none of the business of the federal government under our constitution and that on those grounds you oppose DOMA, just as you do many other extra-constitutional measures.
But no. You couldn't shut the hell up. You couldn't wrap your mind around "this is none of a Presidents business and can only hurt me."
You have a fragile candidacy facilitated only by broad distaste for the incumbent. The nicest thing most GOP folks have to say about you is, reluctantly, "well, he's better than Obama." You may, quite p0ssibly, have screwed the pooch.