Rep. George Radanovich (R-Calif.) is set to announce Tuesday that he will not seek reelection, according to House Republican aides.
Radanovich has missed a series of votes recently, citing his wife's health. She was diagnosed with ovarian cancer in recent years.
Radanovich's office said he would issue a statement at 2 p.m. Eastern time.
Radanovich would become the first Republican this cycle to retire without seeking another office. Four Democrats have done so in recent weeks, leaving seats vulnerable to takeover.
Radanovich's district could also be competitive. Like many California districts, it swung strongly toward the Democratic side in the 2008 presidential election. Sen. John McCain (R-Ariz.) still won 52-46, but the district appears much more accessible to Democrats now than it was earlier this decade.
Former Fresno Mayor Jim Patterson threatened to challenge Radanovich in a primary and appears to be a good bet to enter the race the succeed him.
Radanovich, who was elected in 1994, is just 54 years old.
UPDATE 1:25 p.m.: State Sen. Jeff Denham (R) confirms the reports and says Radanovich has asked him to run in the race to succeed him. Perhaps the congressman wasn't so happy about being pressured by Patterson.
Denham told Jon Fleischman: "I was both surprised and honored when George Radanovich called to tell me of his decision and asked me to consider running to succeed him in Congress. George has served the people of the Central Valley with great dedication and accomplishment for 15 years. He first ran for Congress for all the right reasons, and he is leaving for the right reason -- to spend more time with his family."
Denham had been running for lieutenant governor until earlier this month, but then shifted his focus to the state assembly. The latest race switch will be his second in three weeks.
Fleischman also said other congressmen will line up behind Denham, including Reps. Ed Royce (R-Calif.) and Duncan D. Hunter (R-Calif.).
UPDATE 2:15 p.m.: Radanovich has made it official and has endorsed Denham.
“As many already know, Ethie has been valiantly fighting ovarian cancer for nearly three years. My family needs me, and I intend to be by their side to win this battle.
“It is for this reason that I have decided to not seek reelection to Congress in 2010.
“I am pleased to say that I reached out to State Senator Jeff Denham and asked him to consider running for my seat. Jeff and I share over 100,000 constituents and I have witnessed firsthand the work he has done for our special part of California. After consulting with his family, he agreed to be our Republican candidate for the 19th congressional district."