House Armed Services Committee Chairman Buck McKeon (R-Calif.) will announce his retirement on Thursday, according to two sources close to McKeon.
"Mr. McKeon will be making his announcement tomorrow morning that he'll be retiring," a source close to McKeon tells The Hill.
Democrats are hopeful they could compete for McKeon's slightly Republican-leaning district in Southern California now that he's retiring.
President Obama won 48 percent of the vote there in 2012. Lee Rogers (D), who held McKeon to under 55 percent of the vote in 2012, is running again and had $180,000 in the bank as of the end of September.
McKeon is the latest in a series of senior lawmakers to announce his retirement. A total of 16 congressmen have announced they would not seek reelection at the end of this term.
Rumors have swirled for months that McKeon was likely to retire. His longtime chief of staff, Bob Cochran, left his office in late 2012 and two local Republicans — 2012 congressional candidate and former California state Sen. Tony Strickland, and California state Sen. Steve Knight (R) — had already said they would run if he retires.
McKeon has been chairman of the powerful House Armed Services Committee since 2011 and has been a vocal advocate against cuts to the Pentagon budget stemming from sequestration.
His departure will mark yet another change at the top of the four defense committees in Congress, which all will have chairmen with two years experience or less in 2015.
Both McKeon and Senate Armed Services Committee Chairman Carl Levin (D-Mich.) are retiring at the end of this term. The Appropriations Defense subcommittee chairmen, Sen. Dick Durbin (D-Ill.) and Rep. Rodney Frelinghuysen (R-N.J.), took over the panels after the deaths of Sen. Daniel Inouye (D-Hawaii) and Rep. Bill Young (R-Fla.).
There will likely be a battle for McKeon's chairmanship.
Defense industry officials say that Rep. Mac Thornberry (R-Texas), the vice chairman of the panel, is considered the front-runner to be the next chairman.
Thornberry is also McKeon's preferred pick to take over the committee, according to defense sources.
"Thornberry does all the right things. He does what he needs to for the party; he's well thought of on the committee; and Buck wants him to be his heir apparent,” said one defense lobbyist. "There's no reason to pass him over."
Other senior members of the Armed Services panel are also likely to vie for the chairmanship include Rep. Randy Forbes (R-Va.), who chairs the seapower subcommittee, and Rep. Michael Turner (R-Ohio), chair of the Tactical Air and Land Forces sub-panel.
— This post was updated at 3:45 p.m.