Another senior moderate Democrat is retiring. In a press release, Rep. Bart Gordon, a Democrat who has represented Middle Tennessee for a quarter of a decade, calls the advent of his 60th year of human existence a turning point. The guy wants to spend more time with his family. Gordon tends win re-election handily in a district where Republicans have an edge in national races. Sen. John McCain beat President Obama in TN 06 by more than 20 points. He's faced tough votes this year: on the Pitts amendment regarding abortion coverage in health care, on cap-and-trade (he's chairman of the House Science and Technology Committee), and on the public option -- and he was a target for Tea Partiers in August. The GOP has been searching for a top caliber candidate to challenge Gordon; there are four in the race now: leading the pack are Lou Ann Zelenick, who's already been running radio ads associating Gordon with Speaker Nancy Pelosi, and State Sen. Jim Tracy. Now, Democrats have to scramble to retain the seat.