California state Sen. Tom McClintock on Tuesday entered the GOP primary for retiring Rep. John Doolittle’s (R-Calif.) seat, as two other candidates cleared the way for a titanic battle between McClintock and former Rep. Doug Ose (R).

Former state Sen. Rico Oller and Air Force reservist Eric Egland both left the race and endorsed McClintock, a former gubernatorial candidate and conservative icon who leads in early polling by a large margin.

“If both he and I remain, we run the very great risk of delivering the seat to an unarguably liberal Republican, Doug Ose,” Oller said in a statement. “I find that prospect repugnant to all in which I believe.”

Ose countered by announcing the endorsement of former Golden State Gov. Pete Wilson (R), and his campaign said it was launching a half-million-dollar advertising blitz that it had promised upon McClintock’s entry.

“I am honored to be supported by a Republican who understands the need for active leadership in D.C. and knows the commitment that’s required to get things done,” said Ose, who has also been endorsed by GOP Reps. Dan Lungren, Wally Herger, Duncan Hunter, David Dreier, Jerry Lewis, Ken Calvert, George Radanovich, Darrell Issa, Buck McKeon and Gary Miller.

The winner will likely face retired Army Lt. Col. Charlie Brown, who fell to Doolittle by a narrow margin in 2006 and is the only major Democrat in the race.

Brown previewed a line of attack by noting that neither McClintock nor Ose lives in the district.

“I’m proud to be the only candidate in this race who has lived, worked and raised their family in District Four,” Brown said. “And I’ll put my 35 years of battle-tested leadership up against a group of carpet-bagging career politicians any day.”