In a rematch from 2022, Rep. Ken Calvert - the longest-serving Republican in the state's congressional delegation - defeated rival Democrat Will Rollins in California's 41st District, which was a top target for national Democrats.
Meanwhile, Republicans and Democrats awaited the outcome of vote-counting for other crucial U.S. House districts in California on Wednesday, as the GOP moved within one win of maintaining control of the chamber next year.
Calvert, who was backed by President-elect Donald Trump, claimed his 17th term in a Riverside County district narrowly carried by Trump in 2020.
"This is a hard-fought victory that shows voters want someone who will put results above partisan politics," Calvert said in a post on X.
On Tuesday, Republican Rep. David Valadao's victory in California's 22nd District moved Republicans within two wins of retaining the House gavel, with the tally 216-207 in favor of the GOP, as counting continued in a sliver of races across the country.
With Calvert's win, the Republican tally reached 217.
Several races remained in play in California that could determine control of the House.
California is known as a liberal protectorate - Democrats hold every statewide office, dominate the Legislature and congressional delegation and outnumber registered Republicans by a staggering 2-1 ratio. Still, Republicans retain pockets of political clout in the Southern California suburbs and vast rural stretches, including the Central Valley.