Is the US ready for a Mormon President?
I don't know much about Romney, but I am curious about the "too Mormon" charge. The church seems in recent years to be succesfully remaking its image as a mainstream denomination. The highest-placed Senate Democrat, Harry Reid, is Mormon; one of the most powerful Senate Republicans, Orrin Hatch, is Mormon. With the 2000 Winter Olympics being held in Salt Lake City, the LDS church washed a lot of dirty laundry, the nation and world got a chance to air all of their favorite polygamy jokes, and for the most part, my guess is that the Olympics was a chance for people to work through their prejudices and (mostly) get over them.
That said, a wariness of the church and Mormon individuals still persists.
Religions with on-going revelation tend to have that problem. While less was made of John Kerry's Catholicism that was of Kennedy's, there was still a bit of nastiness when one cardinal threatened to refuse Kerry communion because of his pro-life stance. The Pope's directives about gay marriage and abortion didn't help Kerry's any and probably fed into the general perception of Kerry as insincere. The Mormon church goes even further: the President of the church regularly receives revelation as a prophet on the behalf of church members. The political problem with this kind of theological organization is that the church's official position is easily conflated with the individual's.
And the church's history might alarm some voters. Its history of following its own decrees in the teeth of federal laws (plural marriage, anyone?) is rather recent, and then there's the problematic history with black men being refusing priesthood rights until very late. The Mountain Meadow Massacre will get yet another airing. A Republican Mormon presidential candidate would be asked questions about the early church's centrally planned economy and its communistic "United Order."
The real obstacle would be religious. Southern evangelicals, particularly, have remained actively vocal denouncers of the LDS church's generally anabaptist and antitrinitarian tendencies. Poke around BeliefNet message boards and you'll find plenty of evangelicals who have a serious bone to pick with the Mormon Church's "three persons, one purpose" take on the trinity. Jews have protested the LDS church's desire to baptize-by-proxy their ancestors. And almost everyone gets a little creeped out by temple practices--which the Church hasn't really managed to assuage by the temple previews. The secresy surrounding these huge (and let's face it, often grandiose) buildings makes people suspicious. Oh, and Mormon religious culture, with its strong millenialist tendencies, its veneration of John Milton, and its horror of "priestcraft," has often fairly had somewhat nasty takes on the Catholic Church.
In other words: eventually a Mormon candidate could probably win the presidency, but I don't think it'll happen real soon. The West would go for a Mormon who appealed on the issues and to the party, the NorthEast could possibly go for a Democrat Mormon (maybe with some resistance in the primary), but the South would likely resist a Mormon Republican nomination.