By the time Fred Thompson decides whether or not to join the presidential fray, you will have heard the story of his red pickup truck at least a dozen times. The truck in question is a 1990 Chevy, which the famed statesman-thespian rented during his maiden Senate campaign in 1994. The idea was that Thompson would dress up in blue jeans and shabby boots and drive himself to campaign events around the state. Upon arriving, he'd mount the bed of the truck and launch into a homespun riff on the virtues of citizen-legislators and the perils of Washington insider-ism. For...