Republican U.S. Rep. Andy Barr has filed for re-election in Kentucky's 6th Congressional District.

Barr filed papers with the Kentucky Secretary of State Thursday morning. He is seeking a fourth term in Congress representing a district that includes Lexington, Kentucky's second-largest city.

The district had traditionally been a Democratic seat. But since 1979, it has flipped five times between the two major political parties, most recently when Barr ousted Democrat Ben Chandler in 2012.

Democrats have targeted the seat in their quest to win a majority in the House of Representatives. At least four Democrats say they are running. They include Lexington Mayor Jim Gray, former Marine fighter pilot Amy McGrath, state Sen. Reggie Thomas and Geoff Young, a former state worker who has lost the election twice before.