Fred Thompson isn't the only 'Law and Order' character eyeing the 2008 presidential campaign. Inside Sam Waterston’s efforts to help promote a third-party ticket. The actor Sam Waterston, who plays the hard-hitting assistant D.A. in “Law and Order,” has a confession to make. “I’m a moderate,” he declared in a speech at the National Press Club. “You’re looking at a bird rarely seen in Washington, even in springtime.” Waterston was in town to promote Unity ’08, an Internet scheme to launch a third-party ticket, made up of a Republican and a Democrat, to run together against the two major party...