Political dominoes toppled across California last week, with three Republican retirement announcements, one district switch and an influx of rising stars to the Congressional landscape.

Rep. Elton Gallegly announced his retirement on an early January Saturday morning. That was followed three days later by the retirement of Northern California Rep. Wally Herger. Rep. Jerry Lewis, a former chairman of the Appropriations Committee, announced his retirement Thursday, which led Rep. Gary Miller (R) to run for Lewis’ seat.

The three exits highlighted the leading causes of turnover for the delegation in the upcoming election — redistricting and age — and ensured that at least nine California Members elected in 2010 won’t be returning in 2013.

Democratic Reps. Lynn Woolsey and Dennis Cardoza are retiring; Rep. Bob Filner (D) is running for San Diego mayor; former Rep. Jane Harman (D) resigned in February; and two Democrats will not emerge from the state’s two Member-vs.-Member races.

Reps. Brad Sherman and Howard Berman are facing off in the San Fernando Valley, and Reps. Janice Hahn and Laura Richardson are jousting for a south Los Angeles seat.

Democrats are expected to gain at least a couple of seats, but with more competitive districts this year than the state had over five election cycles in the past decade, estimates range widely from one to six.

The state’s political upheaval was caused by a new independent redistricting process that eliminated the goal of incumbent protection sought in decades past by the state Legislature, which had been charged with drawing the lines until last year. The new process opened the door for new blood in the delegation and additional opportunities for Latinos.

Gallegly’s retirement ensured Rep. Buck McKeon would not face a fellow Republican, though Gallegly could have run in the new Ventura County-based 26th district as well. Lewis’ retirement allowed Republicans to avoid a more likely Member-vs.-Member race in Orange County.

Miller waited only two hours to announce he would run in Lewis’ San Bernardino-based 31st district instead of against Rep. Ed Royce, whom insiders viewed as the favorite for the solidly Republican 39th district.

“The Lewis decision to retire greatly simplifies things for us in California and bolsters our chances dramatically,” California GOP Chairman Tom Del Beccaro said. “What would’ve been a knock-down, drag-out between two well-financed incumbents not only would have bloodied them, but takes resources away from other races.”

With Miller running in the 31st, it “avoids a battle and frees up a lot of resources for us to win some of these other races,” Del Beccaro added.

Miller will now vie for a Democratic-leaning district, but he won’t be alone. San Bernardino County District Attorney Mike Ramos (R) took himself out of the running, but state Sen. Bob Dutton (R) told Roll Call on Friday that he remains “very, very interested and strongly leaning in that direction.” Dutton, who said he’ll likely announce his decision any day now, noted that nearly the entire district overlaps with his state Senate district, which he’s represented for seven years, while Miller doesn’t currently represent any of it.

At the same time, Democrats got their desired candidate for the district in Redlands Mayor Pete Aguilar.

“Jerry Lewis’ retirement takes a seat from being a small opportunity to being a serious opportunity, and we’re marshaling to have a serious candidate run a serious race and make that a pickup for Democrats in California,” said Eric Bauman, chairman of the Los Angeles County Democratic Party. “And it looks like Mayor Pete Aguilar could be just that candidate.”

Miller’s immediate endorsement by the National Republican Congressional Committee led to further speculation that Rules Chairman David Dreier (R) will be the next to announce his retirement. Dreier was left with nowhere to go after the Citizens Redistricting Commission carved up his district.

A Dreier spokesman did not return a call for comment, but the Congressman released a statement after Lewis’ retirement announcement.

“It has been an honor to serve with them,” Dreier said last week of his three retiring colleagues. “We will all continue to work on these and other issues, particularly job creation, throughout the coming year.”

National Democrats welcomed Gallegly’s retirement, which assured that the new 26th district, which leans slightly Democratic and has a 26 percent Latino voting-age population, would be an open seat. Its marginal partisan leaning is attractive to both parties, however, and Gallegly’s exit opened the door for at least two more Republicans: state Sen. Tony Strickland, who is expected to run and is considered a strong candidate, and Ventura County Supervisor Linda Parks.

Democrats were already flocking to the district, including Ventura County Supervisor Steve Bennett, whom Democrats have wanted to run for Congress for some time, as well as Moorpark City Councilman David Pollock, Oxnard Harbor Commissioner Jess Herrera and businessman David Cruz Thayne.

Two open districts affected by GOP retirements that won’t be competitive for Democrats are the 8th in the High Desert, which Lewis could have run for, and Herger’s 1st in the northeastern corner of the state.

Two top Republicans announced in the 8th immediately after Lewis’ announcement: Assemblyman Paul Cook and San Bernardino County Supervisor Brad Mitzelfelt. Because of the state’s new top-two primary format, both could advance to the November general election.

Herger’s exit caused relatively little political disruption, but it led yet another state legislator to run for Congress. Herger endorsed state Sen. Doug LaMalfa, the early favorite.