NASHVILLE, Tenn. (AP) -- Republican Sen. Lamar Alexander is officially launching his re-election bid.

Alexander, who was first elected to the Senate in 2002, previously served two terms as governor and is also a former U.S. education secretary and president of the University of Tennessee.

Alexander has no challengers in his party's primary so far.

Former state Democratic Party Chairman Bob Tuke and former Knox County Clerk Mike Padgett have announced bids for the Democratic nomination.

Nashville businessman Kenneth Eaton and Chris Lugo, who ran as a Green Party candidate against GOP Sen. Bob Corker in 2006, also plan to run.

(Copyright 2008 by The Associated Press. All Rights Reserved.)