I honestly think that a cultural WASP would be perfectly happy with a Catholic, as long as he says everything they want to hear. It's not the 1950s anymore, and Cathoic is "generally Christian" enough for just about anyone in America. Certainly a lot more than Mormon, or what people generally think of as Mormon.
I have a hard time picturing Huntsman becoming the Anti-Romney, simply because from what I can tell most of the social conservatives see him as Romney Lite. Or possibly Romney without the flip-flopping. I don't think the social conservatives will ever cleave to Huntsman just to ward off Romney. If it came down to that, they'd just abstain all together and start railing about how God is going to rain down fire and brimstone after the election because the GOP has lost its way or some shit (I'll leave it to Pat Robertson to come up with the specifics).
Huntsman's only real hope is that he can draw enough of the Gingrich and Romney camps that are fed up with those candidate's own respective baggages and see him as a "close enough" version of what they liked about Gingrich/Romney in the first place.
That was what I was going for, but I didn't really think about the Romney-Lite aspect, and you are correct. In my hypothetical, Huntsman becomes the "moderate" alternative to Romney, for "moderates" who want an all-business candidate and don't want Romney. Obviously that would leave pretty much all of the cultural wing of the party out in the cold, which is how Santorum would survive. If Huntsman comes out of New Hampshire in third or second, it'll be a very fractured four-way race. If it's Santorum, it'll narrow to two (and Paul) pretty much immediately.
I just remember the other reason South Carolina will be an interesting watch. Governor Nikki Haley there rode into office as a Tea Party poster-girl, and
endorsed Mitt Romney back in mid-December and is catching a lot of crap for it. There's a lot of ways you could read that: A pragmatic politician reading the likely future, a case-study of the "Tea Party" ethos being bought out, or maybe just an honest tone-deaf personal decision. I doubt it'll ultimately matter for much in the primary, but it's another fascinating intellectual battleground for the Republican soul. It's worth remembering though that for all of Mitt Romney's financial backing, he's yet to secure the nod from corporate giants like the Koch Foundation.