I think Obama was able to define Romney's campaign for him. He's a Mormon, that's a third class citizen in the Christian family, he was also a popular Mass. Governor. If he were elected I think he would have stayed far away from social issues but the President kept baiting him in. The women's health benefits mandate on private plans with no co-pays or opt outs, changing his views on gay marriage in his last year to distinguish them from Romney's (they were both on board with civil unions previously), not enforcing deportations during an election year but refusing to spend any political capital prior to that on the issue (if you go back to 2008 Barack wanted immigrants to pay a fine, learn english, and get at the back of the line). He backed Romney into a corner where he was forced to play to his base when the only real issue was always economics and scope of government.
The only real answer to the Democrats is a libertarian party regardless of what it's called. Anything based upon religous zealotry or Democrat Lite GW Bush types aren't worth the effort. I'd rather the Democrat run unopposed. It bugs me when the Federal government is pulled into issues that it has no business being involved in.
Romney's problem was not that Obama was able to define Romney's campaign for him, it was that Romeny never defined his own campaign for himself. No one could pin down what he stood for on anything. I will not disput that Mormon is not a full citizen in the Christian Nation, but neither is any other religion. I will say however that the christian right wing did suprise me when the actually did mostly embrace him as their candidate. Mitt did a good job of rarely to never mentioning "mormon' by name.
And from a social issues perspective, I don't agree that it was front and center this election. As a matter of fact, in the days leading up the election I was angry that Obama wasn't hammering mitt on them MORE. Because allowing Mitt to remain silent on it only benefited Mitt. Many many family members of mine sat back and said....seeeeeee mitt isn't anti gay, he never mentions it at all.