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LOS ANGELES (AP) — Republican David Valadao topped the field Tuesday in one of California's marquee U.S. House races, setting up a November showdown with one of two Democrats in a district carried easily by President Barack Obama in 2012.

The 21st District seat in the state's farm belt is a top target for Democrats, as the party seeks to gain ground in a longshot bid to reclaim majority control in the House. Valadeo grew up on a dairy farm in the district, but its registration skews sharply Democratic.

Early primary election returns show tight races for House seats from San Diego to Sacramento. No incumbents appeared in danger.

An 18-candidate free-for-all is underway in a coastal district that includes Malibu and Beverly Hills, where the candidates range from best-selling author Marianne Williamson to gang prosecutor Elan Carr.

Freshman Democrat Scott Peters is trying to hold off several Republicans in his San Diego district. 

And former congressman Doug Ose jumped ahead of several Republicans who want a chance to challenge Democrat Ami Bera in the closely divided 7th District in suburban Sacramento.

In the competitive 26th District in Ventura County, freshman Democrat Julia Brownley will face GOP Assemblyman Jeff Gorell, a former prosecutor who served in Afghanistan.

Under state election rules, only the two candidates who receive the most primary votes advance to the November general election, regardless of party affiliation.

Democrats have a steep climb to seize power in the House and the party needs to flip seats in California to have any hope of assuming majority status next year.

Other competitive contests included the San Bernardino-area's 31st Congressional District, where Democrats are eager to take control of the seat after the retirement of Republican Rep. Gary Miller.

Democratic Party officials are eager for a reprise of 2012, when California provided four of the eight House seats the party gained nationally. Meanwhile, Republicans intend to end their long slide in California and use the state to expand their controlling House margin.

House Republicans have 233 seats and Democrats 199, with three vacancies. Redrawn congressional districts after the 2010 census favored Republicans nationally, and the party that holds the White House historically has lost seats in elections at this point in a president's term. So a change of House control is considered a longshot.

The so-called "top-two" primary could set up fall showdowns between candidates from the same party, which happened in 2012.

Departing House members have provided a handful of open seats, including districts held by long-serving Democrat Henry Waxman and Republican Howard "Buck" McKeon.

California once was a stronghold for entrenched incumbents, where district lines were drawn by political insiders to create lopsided contests that virtually ended competition. But voters shifted the job of crafting district boundaries to an independent commission, and the state now features some of the most competitive House races in the country.

Democrats have been fretting about the likelihood of a paltry turnout that could leave their candidates vulnerable, while Republicans are bargaining that opposition to Obama and his health care overhaul will motivate their ranks. The races played out a time of mixed fortunes for the nation's most populous state, with key issues ranging from immigration reform to health care. The recovery from the recession has been uneven and California's unemployment rate remains among the worst for states.

Bera's district is about evenly split between Democrats and Republicans, and he's the only Democrat on the ballot, making it likely he will survive the primary. Competition on the GOP side has been fierce among tea party favorite Igor Birman, who could become the first member of Congress born in the former Soviet Union, Ose and Elizabeth Emken, who has previously run for the House and U.S. Senate.

The most vulnerable Democratic incumbents in the general election appear to be four freshmen. In addition to Bera, they are Reps. Raul Ruiz from the Coachella Valley, Peters and Brownley.

Democrats have targeted Republican Rep. David Valadao, whose farm-belt district south of Fresno has a Democratic tilt.

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