If you were to quantify the issues that have actually been brought up regarding Mitt Romney's so-called drawbacks, his religion has actually been one of the least mentioned considering that his opposition has so much more "meat" to draw from such as his total income, properties, tax returns, even the issue with his dog Seamus. This being said, his religion will matter very little to the voters if there is anything more interesting than the Mormons to try to get him for.
As far as Obama's race, people underestimate and overestimate this. Whether one is an Obama voter or not, the fact is that it was Obama who had the overwhelming backup and support of the media and many other powerful groups who greatly influenced the population. How could the media not want to cover a man who, if elected President, would make history in the US? Unfortunately and unfairly, and along the same lines, the media did take ugly jabs at the GOP candidates which pointed to the power the media can exert.
The stronger predictor, in the end, will be precisely whoever and whatever the media decides to back. Once the media takes over the psyche of the community, very little else can influence the people, except the use of their own common sense and attention to facts. This latter is what separates the leaders from the followers.