The race to succeed Rep. Henry A. Waxman is emblematic of a fresh wave sweeping across California's politics and, increasingly, the national landscape: intraparty fratricide as a means of upward political mobility.

Four of California's Democrats in Congress lost to members of their own party in 2012, while Republicans did not knock out a single opposition lawmaker. Another Democratic incumbent faces a stiff intraparty challenge in a Silicon Valley district this year, and the clash for the Waxman seat seems destined to be expensive and bloody.

In part, the fighting exists because districts are increasingly partisan, meaning that the only chance to knock off an incumbent rests with someone of the same party.

At best, such fights harden the candidates for cross-party warfare. At worst, they leave bruised relationships, political wounds and, on occasion, a nominee who caters to the party's base at the expense of broader appeal.

PHOTOS: Politics in 2014

In California, there is the added fillip of the so-called jungle primary, in which the top two vote-getters in June move on to the general election regardless of party affiliation. In effect, that means members of one party can continue to battle one another until November. That could be the case for both the Waxman district in West Los Angeles and the seat held by Democrat Michael M. Honda of San Jose.

"How nasty those campaigns get and how vicious they get and how personal they get is going to be an indicator of whether the 'top two' has the real ramification of splitting the Democratic coalition," said Democratic strategist Garry South.

Intraparty battle led to political retribution last year. Steve Glazer, Gov. Jerry Brown's 2010 campaign manager, and other Democratic consultants were blacklisted by the California Labor Federation after they worked against labor's interests in two 2012 Assembly races that featured feuding Democratic candidates.

Bitter intraparty battles among both Republicans and Democrats are becoming more common across the country, as the number of contested districts shrinks. California has independent redistricting, which eliminated blatant gerrymandering that kept districts solidly in one column or the other. However, between the tendency of voters to congregate with those who think like them, and Democratic dominance in the state, more and more races in California are becoming head-to-head Democratic contests.

These battles could get even bloodier in big-ticket statewide races in 2016 and 2018, when the governor's office and perhaps one or more U.S. Senate seats will be vacant. (Senate incumbents Barbara Boxer and Dianne Feinstein, who are up in 2016 and 2018, have not said if they will run again.)

"Republicans have to worry about the possibility in 2018 there are two Democrats running against each other for governor and no Republican even on the ballot," South said.

Intraparty races are already building this year. The most prominent until now has been former Obama administration official Ro Khanna's effort to unseat Honda. Establishment Democrats, from President Obama down, are backing Honda, but Khanna is receiving major support — financial and tactical — from some Obama donors and strategists.

Rep. Eric Swalwell of Dublin, who defeated Democratic incumbent Pete Stark in 2012, is facing a challenge by a fellow Democrat, state Sen. Ellen Corbett of San Leandro.

Stark was one of four incumbents felled by fellow Democrats two years ago. Rep. Joe Baca lost a challenge from Gloria Negrete McLeod of Chino. And after redistricting forced four incumbents into two Los Angeles-area districts, Reps. Howard L. Berman and Laura Richardson lost their offices.

Some Republican-on-Republican races are emerging in districts where their voting strength is consolidated.

In a solidly red Orange County district, a three-way fight is underway to replace Rep. John Campbell of Irvine, featuring County Supervisor John Moorlach, retired Marine Col. Greg Raths and state Sen. Mimi Walters of Irvine.

Some Republicans say the new rules could benefit them by offering a chance in districts in which they never would have had a shot under the old system. If the right candidate surfaced, the Waxman seat could offer Republicans "a fighting chance in what would be an otherwise unwinnable seat," said Adam Mendelsohn, a political strategist and advisor to former Gov. Arnold Schwarzenegger.

He acknowledged that any Republican would face an uphill battle because of the district's makeup. But if Democrats damage themselves in a protracted battle, he argued, a credible center-right candidate with financial resources could pick up voters dismayed at the spectacle.

So far, no Republican candidate of his description has materialized, although wealthy Republican-turned-independent Bill Bloomfield, who challenged Waxman in 2012 and won 46% of the vote, may run again. (Democratic entrants include former Los Angeles City Controller Wendy Greuel and state Sen. Ted Lieu of Torrance, with others circling the race.)

"The feeling is 2014 is really where you see it, and the Waxman race is an opportunity for the power of the 'top two' to come into play," Mendelsohn said. "The question is whether the candidate will align with the opportunity."

Reed Galen, a Republican strategist, agreed.

"There are only so many Democratic votes, and the Democrats are all going to beat the you-know-what out of each other," he said.

Multi-candidate races are unpredictable, strategically fraught and subject to bank-shot calculations, since a move against one opponent, if it offends voters, could benefit a third.

Such unexpected ricochets produced a surprise result in 2012 in an Inland Empire congressional district. Democrats had expected to take the seat, but four Democrats split the party's vote in the June election, sending two Republicans into the general election. The winner was conservative Gary G. Miller.

"Nobody expected that congressional race," said Paul Mitchell, a Democratic redistricting expert. "You had a situation where four Democrats split the vote, very low Democratic turnout, and voila."

This year, the same forces are at play. Four Democrats are running for the Miller seat, although national party strategists are trying to winnow the field to increase a Democrat's chances of taking the district. But with the top-two primary, no candidate has seen an incentive to leave — all they need to do is to come in second to move on to November.

seema.mehta@latimes.com

Times staff writer Jean Merl contributed to this report.