Most Mormons I know who are supporting him are doing so because he shares their values, NOT because they are Mormons. They don’t support Harry Reid, for example, even though he is also a Mormon.
However, it is true that I have not met a Mormon who holds Romney’s faith against him.
That's why I say it's a paradox. It may be true that they don't support him just because he is a Mormon, but making statements that Romney would be the first Mormon President and that would be good for the LDS church or even just saying Mormons have good family values so you should vote for Mitt if you are a conservative makes a statement, on the other hand, that religion has nothing to do with politics seem absurd.
Let's have a discussion about how religion would have nothing to do with our vote in a race against an atheist and a Christian or even a Muslim and a Christian. Religion does make a difference. It might not be the primary difference, but for most people it is always a factor somewhere along the line in the decision process no matter what faith they practice. You can make lofty idealic speeches, but at the end of the day, if we are honest with ourselves, religion can and does factor in to our decisions.