JACKSON, Tenn. (AP) — Herman Cain is firing up the crowd at a tea party rally in this West Tennessee town when the generator powering his sound system shudders to a halt. Cain stands awkwardly for a few moments then suddenly begins to sing. Slowly at first but gaining in speed, he belts out "Impossible Dream" in the rich baritone he's honed in church choir. "You know, when it's your rally, you can do what you want to do!" Cain says as he finishes with a raucous laugh. The 500 or so supporters who have jammed the strip mall parking...