(1) I saw a list of Romney's foreign policy advisers. About one third of them are Jewish!
(2) Is Mitt Romney (a Mormon) himself a Christian? I don't want to get into a theological argument, but it's safe to say that some Christians would answer "NO" to that question. Besides, that isn't an issue in this race.
(3) FWIW, I can tell you from my Jewish perspective that Mitt's father George was well liked and respected by the Jewish community in Michigan when he was governor there. There was no religious friction whatsoever.
The Republican Party has Christian, Jewish, Mormon, and non-religious members.
The Democrat Party has Christian, Jewish, Mormon, and non-religious members.
Neither party has any sort of religious monopoly.