Why don't many Christians consider Mitt Romney a Christian?

There are a core set of beliefs that Christian demoninations agree upon...mormonism does not share them. As examples, the virgin birth & holy trinity.

I don't consider him to be a Christian for the reasons given in the posts above, but I do consider him to be a man of God. I happen to believe that all religions are true and accurate as long as they focus upon the one and only God. So much of everything else is a consequence of man's interpretation mixed with an intermingling of man created laws. I don't pretend to know who is right and who is wrong among us, as I am hardly qualified to act in the place of God and condemning others for their particular beliefs is, imo, not my place nor, a responsibility that I would ever want to have.

Because he's a Mormon. They're part of the Restorationist branch of Christianity, and most orthodox (small 'o') Christians don't think it's legitimately Christian since it changes so many basic doctrines.

Most Christians dont consider dark skin a curse.

Largely due to the fact that he is a Mormon and thus wears magical underpants and will inherent his own planet upon his death. I wish I were making this up, but sadly I am not.

God told us to beware of false prophets and I think Joesph Smith was one of them.just because someone said Jesus appeared to him it doesn't make it a fact.

Because they believe the have living prophets.

http://lds.org/study/prophets-speak-today?lang=eng

Once my wife found this out we both spoke and said "sounds like a cult."