COLUMBIA, S.C. - When Republican presidential hopeful Fred Thompson walks down the aisles of a gun show Saturday in Charleston, the game he's hunting won't be hard to spot. The former senator and actor is looking to differentiate himself from rivals Rudy Giuliani and Mitt Romney - and use his appeal as a "country boy from Tennessee" who knows NASCAR and hunting to portray the city slickers as out of step with this early voting state's residents. There is little doubt gun rights are a tough issue for the front of the GOP pack. Former New York Mayor Giuliani has...