Rep. Brad Sherman (D-Calif.) defeated fellow Democratic Rep. Howard Berman in their member-vs.-member match-up.
It was a nasty campaign, with the two lawmakers almost coming to blows during a debate and having to be separated by a police officer.
The redistricting process put the two men in the same seat, which contained much of Sherman's old territory. Under California's new primary system, the top two vote-getters, regardless of party, move on to the general election.
Democratic leadership indicated a preference for Berman, with Rep. Steny Hoyer (D-Md.), the No. 2 in leadership, endorsing him. Berman also had the endorsement of prominent Republicans like Sens. John McCainJohn McCainWhy lobbyists should welcome a transparent presidential transition Experts warn weapons gap is shrinking between US, Russia and China McCain delivers his own foreign policy speech MORE (R-Ariz.) and Lindsey GrahamLindsey GrahamTroops question rules for ISIS medal The beginning of the end for Ted Cruz Graham: 'Lucifer may be the only person Trump can beat in a general election' MORE (R-S.C.), who cited his work on the House Foreign Affairs Committee.
Sherman, meanwhile, had the support of former President Clinton.
—This story was updated at 5:28 a.m.