Fred Thompson's easygoing, no-nonsense style is clearly his strength and undoubtedly has helped him soar in presidential polls. It may only get him so far. Sooner or later, the all-but-declared candidate will have to answer the question: What else do you offer? ''Smooth is good, but sometimes nitty gritty is essential,'' says Tucker Eskew, a Republican strategist unaligned in the race. ''He'll be tested (but) he has a little time.'' Indeed, the actor and former Tennessee senator has bought himself a grace period; he hasn't yet officially joined the 10-man GOP field. He's raised at least several million dollars, assembled...