NASHVILLE (AP) — Democrat James Mackler says he's dropping out of the U.S. Senate race in Tennessee to replace Sen. Bob Corker, a move that appears to clear the path to the Democratic nomination for former Gov. Phil Bredesen.

Mackler said in a news release he's "stepping back" from the race, but will stay active with a political action committee named Believe in Service. The Nashville attorney and Iraq War veteran says the committee will support federal candidates who will protect and expand national service programs.

In a statement, Bredesen said he admires Mackler's commitment to service to the nation and complimented his political action committee idea.

Corker, a Republican, is retiring from the Senate.

Major Republicans in the race to succeed him are U.S. Rep. Marsha Blackburn and former U.S. Rep. Stephen Fincher.