It will be the same for *any* Republican. The Dem base will never vote Republican.
Newt has a FAR, FAR better chance of getting crossover Reagan Democrat votes than either Romney or Santorum. He’s got the “drinking buddy” populist vibe for the blue collar types and he’s got an intellect that could appeal to the suburban elites (although they’re less likely to cross due to the whole thinking Republicans are evil thing).
Obviously Ron Paul could get crossover votes since he holds the foreign policy views of Dennis Kucinich.