A snapshot of key House races in the California primary

LOS ANGELES (AP) — Republicans suffered a string of devastating losses in California U.S. House races in 2018, ceding seven districts to Democrats, including four all or partly in the former GOP stronghold of Orange County. With the resignation last month of Republican Rep. Duncan Hunter, the GOP now holds only six of the state's 53 House seats. But Republicans hope to regain ground in 2020 and prove the party can still win in a heavily Democratic state that is the front of the so-called Trump resistance. Some key races to watch:

BELLWETHER BATTLE

Democrat Katie Hill grabbed the swing 25th District north of Los Angeles in 2018 by toppling Republican Rep. Steve Knight. But Hill is gone — she resigned amid a sex scandal and House ethics probe — and Knight is back trying to regain his old seat. It will be a nationally watched fight. Another leading Republican is Mike Garcia, a former fighter pilot who has raised over $1 million and is being backed by local Republican parties. Gov. Gavin Newsom and much of the Democratic establishment have lined up with state Assembly member Christy Smith, one of six Democrats on the ballot, including progressive online news personality Cenk Uygur. And there is a risk voters might get confused. The race will be on the ballot twice, once for a special election to fill the seat for the remainder of 2020, and a second time for the primary election that will decide which two candidates advance to the November general election. If no candidate tops 50% of the votes in the special election, a run-off between the top two will be held in May.

PRIMARY OVERLOAD

Eleven Democrats are among 15 candidates on the ballot in San Diego County’s strongly Democratic 53rd District being vacated by retiring Rep. Susan Davis. The crowded Democratic field includes San Diego City Council President Georgette Gomez, who has been endorsed by the state Democratic Party, Sen. Bernie Sanders and Justice Democrats, the political group that helped elevate New York Rep. Alexandria Ocasio-Cortez to Congress. There's also former Marine Capt. Janessa Goldbeck and Sara Jacobs, the granddaughter of billionaire Qualcomm co-founder Irwin Jacobs.

FIGHT FOR THE FARM BELT

In the Central Valley’s 21st District, Republican David Valadao is among the candidates trying to take the seat from Democratic Rep. T.J. Cox, who pulled off a 1-point win over Valadao in 2018. The farm-belt district has a significant Democratic registration edge, but Valadeo, a dairy farmer and former state legislator, easily carried it in 2016, in part by focusing on water issues critical to agriculture. In the agriculture-heavy 10th District, freshman Democratic Rep. Josh Harder is facing challengers from both parties.

2018 REMATCH?

Another potential rematch is shaping up in Southern California’s closely divided 39th District, where Democrat Gil Cisneros bested Republican Young Kim in 2018. They are on the ballot again this year. Both parties see the Orange County district, which has a 2-point Democratic registration edge, as important to the overall control of the House.

VACANCY SIGN

Rep. Duncan Hunter pleaded guilty to a corruption charge and resigned in January, further roiling an already unpredictable race for San Diego County’s Republican-leaning 50th District. Democrat Ammar Campa-Najjar is back on the ballot, after coming close to unseating Hunter in 2018. Among the leading Republicans, former Congressman Darrell Issa, who dogged President Barack Obama’s administration when he headed the House Oversight and Government Reform Committee, is trying to return to Washington after representing the neighboring district for nine terms. He’s facing stiff competition from fellow Republicans Carl DeMaio, a former San Diego city councilman and local radio host, and state Sen. Brian Jones, who highlights that he’s the only major Republican candidate who lives in the district.

BEACHFRONT BRAWL

Freshman Rep. Harley Rouda was one of seven California Democrats who seized Republican-held House seats in 2018, a rout that underlined the state’s well-established reputation as a Democratic stronghold. Republicans are determined to regain that turf and his main challenger in the seaside 48th District is Michelle Steel, who heads the Orange County Board of Supervisors and is married to GOP national committeeman Shawn Steel. The district has a GOP registration edge, and it’s expected to be a marquee fight in November. Both candidates — among six on the primary ballot — have deep pockets and long lists of endorsements.

ELIZABETH WARREN PROXY

Rep. Katie Porter comes from the progressive wing of the Democratic Party — the law professor is a protege of Elizabeth Warren and a co-chair of the Massachusetts senator's presidential campaign. In 2018, she grabbed the Republican-held 45th District in the heart of what was once California’s Reagan country. Porter is the only Democrat on the ballot but a handful of Republicans are dueling to advance to November in the GOP-leaning district, including Laguna Hills City Councilman Don Sedgwick, Yorba Linda Councilwoman Peggy Huang and Lisa Sparks, dean of Chapman University’s School of Communications.