My first choice is the dream of a brokered convention.
Absent that, it has to be Santorum. Romney is bad, but we've survived Romney types before. Newt is the worst of both worlds - I trust him as a 'conservative' as far as I can throw his fat butt, he's an unstable megalomaniac, he's the epitome of the corrupt establishment we've been fighting and he has opposed limited government conservatism and conservatives for years, and he's a sure loser against Obama.
Although you said this about Newt, this is how I view Romney.