LOS ANGELES (AP) — The outcome in a string of highly competitive California U.S. House races will play into control of Congress next year, potentially helping Republicans seize control or providing a Democratic buffer as the party struggles to maintain its teetering majority.

The stakes were spotlighted last week, when President Joe Biden traveled to Southern California to campaign on behalf of endangered Democratic Rep. Mike Levin, whose district straddles Orange and San Diego counties. It was Biden’s second trip to California in less than three weeks. Meantime, Vice President Kamala Harris was in Los Angeles for a rally Monday to urge Democratic voters to get to the polls.

Republican leaders believe as many as five districts in the state could swing their way — enough to give the GOP the House gavel in a midterm-election year when voters typically punish the party that holds the White House. Should that happen, Republican Rep. Kevin McCarthy of Bakersfield would be in line to replace Speaker Nancy Pelosi of San Francisco.

For their part, Democrats are eager to claw back four House districts they surrendered in 2020 and hope to gain more to pad their dominance in the state congressional delegation. Republicans hold only 11 of the state’s 53 seats, which drops to 52 seats next year because California’s once-soaring population growth has stalled.

Overall in the House, there are 220 Democrats, 212 Republicans and three vacancies.

Competitive districts are something of a rarity in heavily Democratic California and cut against its national reputation as a liberal stronghold. But pockets of conservative strength remain, even as Democrats hold a nearly 2-to-1 statewide edge in voter registrations.

The contests are being fought over issues that are shaping races around the country.

Democrats are stressing abortion rights and labeling GOP rivals “extremists” in a party still largely under the sway of former President Donald Trump. Republican candidates are faulting Biden and a Democratic Congress for inflation, rising crime and the long-running homeless crisis.

The main battlegrounds are Orange County — a suburban expanse south of Los Angeles that was once a Republican stronghold but has become increasingly diverse and Democratic — and the Central Valley, an inland stretch sometimes called the nation’s salad bowl for its agricultural production.