Razib at Gene Expression has an interesting post about Mitt Romney and Mormonism.
Politically, what it boils down to is, that Mormons are too... different to have a good chance of winning a Presidential election, in particular,. the evangelical base of the GOP would place a prohibitive obstacle on a Mormon getting the Republican nomination.
I will say that I don't think, as some do, that people will be unwilling to elect a Mormon primarily because of some paranoid conspiracy-mongering that the Mormons will try to take over the world, or some such thing, similar to what the concerns were in the 1950s and before about a Catholic President giving the reins of the country over to the Pope. Rather, I think that a large number of people will find the Mormon belief system strange and shy away from a Mormon as being too different; even a lot of the evangelicals will be against a Mormon as president more out of a distaste for Mormon beliefs rather than because they see him as a threat per se.
In any case, as razib points out, it isridiculous for people in the media to talk about Romney as a possible contender without discussing the elephant in the room; much like it is annoying when people laud Giuliani as the candidate for 2008 without considering the fact that he has irreversibly alienated gunowners and the religious right.
That is all.