SACRAMENTO . (AP) — The California Democratic Party and labor unions vowed not to back down any time soon after their candidate lost a costly state Senate race in the San Francisco Bay Area this week.

Orinda Mayor Steve Glazer, a business-backed moderate, defeated fellow Democrat Susan Bonilla by a significant margin in a special election for the 7th Senate district.

Party officials and union leaders blamed higher Republican turnout for their loss, and their statements suggest another scorching fight when Glazer will have to run again next year when the seat comes up for re-election.

“We will not back down from races like this in the future, and Democrats will go to bat for our endorsed candidates who put the needs of working and middle class families first,” California Democratic Party Executive Director Shawnda Westly said in a statement after the race was called.

Glazer said Wednesday that he remains committed to the party and is looking forward to building relationships with both Democrats and Republicans in the Senate.

“The campaign characterizations were harsh and I hope that we can put aside the campaign weaponry and focus on the important common ground of governing,” he said in an interview.

Senate President Pro Tem Kevin de Leon, D-Los Angeles, who did not endorse either candidate, reached out to congratulate Glazer.

“We look forward to welcoming our new colleague and moving boldly ahead with a Democratic agenda that continues California’s progress,” de Leon said.

With all precincts reporting Tuesday night, Glazer had 54.6 percent to 45.4 for Bonilla.

The race between Glazer, a longtime adviser to Gov. Jerry Brown, and Bonilla, an assemblywoman from Concord, drew lots of attention and money — $7 million. Much of the spending came from outside groups that set up their own committees to fund attack mailers and TV commercials on both sides.

Both candidates positioned themselves in the mold of Brown, who did not endorse either.

The party and labor unions were upset that Glazer worked for a Chamber of Commerce-funded committee in 2012 that sought to unseat incumbent Democrats in the Legislature and replace them with Democrats considered friendlier to business interests.

“Our opponent received less than 30 percent of the Democratic vote, which will not be sustainable in future elections in a Democratic-leaning district,” said Jon Youngdahl of the labor-funded Working Families Opposing Glazer 2015 Committee.

Democrats have nearly 44 percent of the registered voters in the 7th Senate District, and Glazer sought to attract Republicans and independents.

Glazer replaces Mark DeSaulnier, who was elected to Congress.