And the last serious DNC nominee who wasn't a mainstream Christian was...?
Hell, by having a serious contender who's a Mormon, the GOP's shown more diversity on the issue than the DNC has, so really, you ought to voice your support by voting GOP this election cycle. Unless, as Loki postulated, this is just your attempt to convince yourself and/or others that you're "open minded," when you're about as close-minded as can be.