A Mormon would have a much easier time winning as a Dem, not as a Rep. Both Mormons and conservative Protestants are natural Republican electorate, but the former are much more numerous, and from their standpoint he is not a Christian - not something they would take lightly. Furthermore, in the general election his Mormonism is gaining him few votes: most of his correligionists would vote for a Republican anyway - whereas a Mormon Dem (against a protestant Rep) would easily carry Nevada
You mean like Harry Reid?