I have doubts as to whether Romney's mormonism was significant enough to change one million votes, or more importantly, a single state. Even if that was a part of it, over all it's that voting for a lesser evil does not inspire enough of the 40% in the middle, who do not vote straight party and can be swayed by their perceptions at the time. It's identification with people that makes the big difference; that is, liking who they are and/or perceiving them as "one of us." While few besides Mormons identify with a Mormon, many identify, or 'like,' a person of self-made success. However, Romney was too rich and wasn't really perceived as self-made in that way. So IMO there was too much more involved to say being a mormon kept him from being elected.
It's quite early to start considering this, but Texas elected a new Senator, Republican Ted Cruz, son of a Cuban who fled to Florida. With the identificatio factor being so important,.. yes, he might be candidate to consider in the future. I don't know much about him yet, but we'll see. Or perhaps the ticket needs to be a Florida/Ohio pres./VP, at least one black or hispanic. But 2 white men whose own states won't vote for them may never work again.