A level of fail like we saw with the Romney campaign has many, many reasons.
A certain number of votes hang on each issue, true. But Romney's open contempt for "social conservatism" (i.e. conservatism) lost the single most critical voting block that any Republican needs to win. Just losing this one group cost him, cost us, the United States, quite possibly.
Apart from the fact that Romney was the wrong guy for this campaign and for this opponent, I am certain (as with ALL Conservative losses) that voter fraud was significant to the outcome. Romney is a relic of a relic party. Who would or could see that succeeding? If you don't even look at any other factors, this would sink the chances of ANY candidate. Romney is "OLD" politics. If nothing ELSE, the nomination and subsequent election/ RE election of "O" have demonstrated that "OLD" politics will NOT succeed any more.
In the Republican primaries Romney was a bare fisted brawler that took no prisoners. He was ruthless. In the election he was milk toast. Nice guys finish last in an election with the exception of Ronald Reagan. Reagan destroyed his opponents with humor and logical conservative principles.