The Daily Dish has a post* about the NRA's dedicated campaign against the democratic party, out of all proportion to Democrat's actual views on gun control (mostly, they don't care anymore -- gun control seems less important than it did during the murder explosion of 1984-1994). I have little to add, other than to say that it is true in my experience as well. Moreover, I feel like the NRA has gotten more partisan after Heston handed off the reigns to Wayne LaPierre -- rather than being a single-issue lobby it seems like another arm of the republican party, dedicated to marshalling gun owners to support Republican causes. And, of course, enrich the NRA's own coffers.
*This is another good article.