This is, I believe, largely because the hunters’ lobby prevailed upon Santorum in Pennsylvania. To read the text Santorum supplies on his website in documentation of his claim to be a 2nd amendment supporter — you’d think it was all about harvesting game.
Newt is not perfect, but he seems at least to get the self-defense intent that the drafters of the 2nd amendment wanted.
At least Santorum was responsive to his constituents. Let's take a look at what Newt's folks in Georgia have to say: