Who Will Win Control of the House in 2024? California May Hold the Key.

As Democrats look to wrest control of the U.S. House of Representatives in November, their fight will fully begin with Tuesday’s primaries in California.

And their immediate trouble is not Republicans. It’s Democrats themselves.

In the Republican-held Central Valley district stretching from Bakersfield to Fresno, which would have favored President Biden by 13 percentage points in 2020, a battle between two Democrats has become so personal that some in the party fear they could divide the vote, leaving the incumbent, Representative David Valadao, competing in November against another Republican running to his right, Chris Mathys.

With so few truly contested seats to fight over this year, the prospect of an early lockout in California — where the top two finishers regardless of party affiliation compete in the general election — has brought out some heavy hitters, including Dolores Huerta, the 93-year-old labor and civil rights leader who co-founded the United Farm Workers with Cesar Chavez in 1962. She is suiting up again on behalf of former California Assemblyman Rudy Salas, the top choice of institutional Democrats. So is California’s governor, Gavin Newsom, who will rally voters for Mr. Salas on Sunday in an effort to box out the other Democratic candidate, State Senator Melissa Hurtado.

“I’m scared,” Ms. Huerta said on Thursday from the unassuming offices of her foundation, which is based in Bakersfield. “We need to do a lot more work.”

Control of Congress could be at stake. Of the 16 House districts won by Mr. Biden but currently in Republican hands, five are in California, making the state a linchpin of the party’s hopes of retaking the chamber, where Republicans currently hold a three-seat majority.

“It’s going to come down to these tossups, and Democrats would have to win around two-thirds of them to take the majority,” said Erin Covey, the House analyst at the nonpartisan Cook Political Report.