"It has been a great honor to spend so many years in public service, striving to make a difference for Southern California families. While there is still a lot of work to be done, it is now time for me to pass the baton. I will not seek re-election to Congress at the end of this term," Miller said in a release on Wednesday.
Associates cited a difficult and nasty custody battle over Miller's two grandchildren with a former daughter-in-law as a major reason for his decision not to run again.
Miller, who was first elected to Congress in 1998 representing the wealthy and heavily Republican Orange County, was redistricted inland in 2012 but managed to win the race anyway thanks largely to a quirk in California's election law that allows the top two vote-getters in a primary to run in the general election regardless of party affiliation.
Miller and another Republican were the top primary vote-getters, meaning general election voters in a district President Barack Obama won with 57 percent didn't have a Democrat on the ballot to choose, Roll Call reported Wednesday.
A deep primary field for the Democrats this year promises that will be unlikely -- and all but assures the party will pick up Miller's seat in November's general election, The Hill said.
Democratic primary candidates include Redlands Mayor Pete Aguilar, attorney Eloise Gomez Reyes, who is running with support from the women's rights group Emily's List and former Rep. Joe Baca, who previously represented part of the district east of Los Angeles and is eyeing a potential comeback.
National Republican Congressional Committee Chairman Rep. Greg Walden, R-Ore, thanked Miller for his service. His statement notably lacked information on the GOP's plan to hold the seat, a tacit acknowledgement it is probably a lost cause, The Hill said.
Notable deaths of 2014 [PHOTOS]