LOS ANGELES (AP) — Several vulnerable U.S. House freshmen survived tight contests in California’s congressional races, as Democrats sought to gain ground in the party’s longshot bid to reclaim majority control in Washington.

Tuesday’s primary contests in the nation’s most populous state sent pairs of candidates to November runoffs and foreshadowed what will be costly, toss-up battles this fall.

In the 52nd District in San Diego, where Republicans hold a slight registration edge, freshman Democrat Scott Peters headed to a November match-up with former San Diego City Councilmember Carl DeMaio.

In a marquee race in the state’s farm belt, Republican Rep. David Valadao topped the field and set up a November showdown with Democrat Amanda Renteria in the 21st District, which was carried easily by President Barack Obama in 2012. He’s seeking a second term. Renteria, the daughter of an immigrant farmworker, is a former aide on Capitol Hill whose candidacy is being backed by national Democrats.

Incomplete primary election returns show tight races from San Diego to Sacramento.

An 18-candidate free-for-all was 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, a Republican.

With partial returns, Carr grabbed a lead in the strongly Democratic district, held for decades by retiring Rep. Henry Waxman. The contest among 10 Democrats was shaping up as a close race between state Sen. Ted Lieu and former Los Angeles Controller Wendy Greuel.

In other top races:

— Former congressman Doug Ose claimed the second spot, ahead of two other Republicans, to earn a chance to challenge freshman Democrat Ami Bera in November 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 in November, a former prosecutor who served in Afghanistan.

— A potential Democrat-against-Democrat runoff was taking shape in the suburban San Francisco 17th District, were seven-term Rep. Mike Honda was running ahead of Ro Khanna, a former Obama administration appointee.

— In the San Bernardino-area’s 31st Congressional District, Democrats are eager to take control of the seat after the retirement of Republican Rep. Gary Miller. But Iraq War veteran and security consultant Paul Chabot, a Republican, advanced to the runoff, with several candidates dueling for the second trip to November.

Under state election rules, only the two candidates who receive the most primary votes advance to the November general election, regardless of party affiliation. Along with the Honda race, the so-called “top-two” primary appeared likely to set up fall showdowns between candidates from the same party in several districts, which happened in 2012.

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. 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.

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 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. Ruiz, an emergency room doctor before his election to Congress, will face state Assemblyman Brian Nestande.

House Democratic leader Nancy Pelosi was claiming nearly three of four votes in her San Francisco district and will be heavily favored over Republican John Dennis in November.