That old National Rifle Association TV ad in which Magnum P.I. actor Tom Selleck says, "I am the NRA" might be making a comeback. That's because he's being talked about as the replacement for former five-term NRA President Charlton Heston, the Moses portrayer who is afflicted with Alzheimer's disease. NRA insiders like the idea of promoting Selleck, an off-and-on NRA-er since he was a kid and now one of 76 board members, to the top job....