Democratic candidates also extended their leads in the state's two remaining unresolved U.S. House races, in San Diego and Sacramento, but those contests remained too close to call.
In Bono Mack's Riverside County district, updated vote totals gave Ruiz a nearly 7,300-vote lead out of about 182,000 cast. The race in the desert communities near Palm Springs was one of this year's hottest congressional battlegrounds as both candidates drew millions of dollars in outside spending.
"I believe that this election sends a message that it's time to put an end to partisan gridlock," Ruiz said. "My door is always open to everyone. If you have a good idea—Democrat or Republican—I want to hear it."
He said when he gets to Washington he will focus on health care, jobs, education and renewable energy.
Bono Mack served eight terms after winning an election in 1998 to fill the seat of her late husband, entertainer Sonny Bono. Her current husband, GOP Rep. Connie Mack IV of Florida, lost his bid for the U.S. Senate.
In a statement to supporters, she congratulated Ruiz and said she was looking forward to starting a new chapter in her life.
"Thank you for giving me the distinct honor of serving in the United States House of Representatives for
In the Sacramento area, Republican Rep. Dan Lungren fell farther behind Democratic physician Ami Bera. After updated vote totals were released Friday, she led by 1,779 votes out of nearly 209,000 cast. Elections officials said there were still about 100,000 votes to be counted in Sacramento County, but it was unclear how many of those fell within the 7th Congressional District.
The situation was the same in San Diego, where GOP Rep. Brian Bilbray lost ground Friday to challenger Scott Peters. Bilbray was 1,334 votes behind with more than 220,000 cast and an unknown number yet to be counted.
County registrars have 28 days after the election to finalize results under California law, but any candidate or voter can ask for a recount within the following five days. Should that occur, local elections officials can appoint four voters to oversee a special recount board, a process that could take weeks to finalize.
California's congressional races were much more competitive this year after an independent panel redrew the district boundaries in 2010, the same year the U.S. Supreme Court struck down limits on outside political spending.
State congressional races drew intense interest nationally, after gerrymandered strongholds were transformed into free-for-alls rich with campaign cash from groups as varied as Planned Parenthood and Americans for Tax Reform, headed by low-tax crusader Grover Norquist.
Super PACs and other outside groups flooded California's House races with more money than any other state under new rules allowing unrestricted outside political spending. By Tuesday, spending had reached nearly $54 million, according to the Center for Responsive Politics.