Actually, I do think that the gun vote was fragmented. Fragmented enough, at least... Say you've got 5,000,000 NRA votes... I'm guessing that at least 10% of them went toward fringe or protest candidates, and likely a sizable percentage also voted Obama based on other issues (like, doh, change, you know?). Or just didn't vote.
All they needed to was have good voters do nothing.