Andrew Sullivan looks at the issue of whether Mormons are Christians here.
For my part, I don’t much care one way or the other, but I don’t think there can be a great deal of doubt about it. In the course of two thousand years Christianity has long since come to mean much more than those texts that some of its early leaders chose to regard as definitive. Naturally, there are many outgrowths of this now wildly varied religion that some Christians will find wanting. And they are perfectly entitled to do so. Those, however, are issues best left to the sectarians. To an outsider, at least, Mormonism is clearly a part of the greater Christian family.