AMES, Iowa - Fred Thompson says his often-dour demeanor simply reflects his seriousness about the issues facing the country. ``I'm just Fred,'' he says, and the image that's served him through a successful political career won't be changing. Thompson, who played a tough-minded and gruff district attorney on television's ``Law & Order,'' offers precisely that image as he campaigns for the GOP presidential nomination. He's generally serious and direct, with little of the backslapping and joking of many of his rivals. ``I laugh when I am amused and I'm amused a lot,'' said Thompson, in an interview with The Associated...