As a group, political reporters are far more secular than the rest of the country, leading them sometimes to misrepresent or underappreciate the impact of religion on voting. I think there is some informative shoe leather reporting undone about how Mormons are perceived by GOP voters.
When I talk to Christian Evangelical friends who are active in Republican politics, their first concern about Romney is not Massachusetts’ health care program and their first concern about Huntsman is not that he worked for President Obama. Rather, they just don’t feel comfortable with the idea of a Mormon President. They generally do not consider Mormons to be Christian and harbor deep distrust about much of LDS practice and beliefs. This Pew poll is a bit out of date, but check out the subsection on GOP Christian Evangelicals to get a flavor of these attitudes.
I don’t see how a Mormon candidate gets out of closed GOP primaries in states like South Carolina and Pennsylvania which have high proportions of Evangelicals. And it’s even worse when they are two candidates competing for the same subset of such voters who are willing to vote for a Mormon.
The history here is interesting. At the wonderful moment in 1854 when the Republican party came into existence and catapulted the career of the man who became perhaps our greatest President, its founders pledged to wipe out “the twins relics of barbarism”. One of those of course was slavery, but few people recall that the other was Mormon polygamy.