A labor union that represents more than 45,000 Kaiser Permanente workers statewide will continue to do so after prevailing in an election Thursday with more than 58 percent of the vote.

Service Employees International-United Healthcare Workers (SEIU-UHW), the largest healthcare union in the western states, beat a smaller challenger, the National Union of Healthcare Workers (NUHW), which had nearly 41 percent.

One percent of the Kaiser workers voted for no union.

The election under the auspices of the National Labor Relations Board was billed as the largest private sector union election in the United States since 1941 at the Ford Motor Company.

SEIU-UHW represents about 1,390 technical and clerical workers at Kaiser facilities in Santa Rosa and Petaluma.

Its victory means that an existing contract with Kaiser will last through 2015.

The pact, negotiated in 2012, included 12 percent wage increases and employer-paid health care with no cost increases, SEIU-UHW said.

The two unions engaged in a hardball battle over rights to represent the workers at about 250 Kaiser hospitals, clinics and other facilities throughout California.

The workers at stake include most Kaiser employees who are not management, doctors or registered nurses.

SEIU-UHW's total membership exceeds 150,000 workers, dwarfing NUHW with 10,000 members.

In a press release, SEIU-UHW described the outcome as a "stinging defeat" for both NUWH and the 18,000-member California Nurses Association. The two groups formed an alliance in January.

NUWH has has challenged SEIU-UHW in dozens of elections over the past four years and has lost nearly 97 percent of the time, SEIU-UHW said in a statement.

NUHW said that the larger union prevailed through a campaign of "fear, intimidation and collusion with management."

Kaiser, an integrated health care system with more than 7 million members statewide, remained neutral in the union dispute, a spokesman said.

"We fully supported the NLRB's election process, because we respect the rights of our employees to choose whether they want to be represented by a union and, if so, which union will represent them," Marc Brown said.

Thursday's result echoes an election in 2010, when 61 percent of Kaiser workers chose to remain with SEIU-UHW.

The NUHW filed a complaint with the Labor Relations Board alleging unfair tactics by SEIU, and an administrative law judge ordered a new election.

You can reach Staff Writer Guy Kovner at 521-5457 or guy.kovner@pressdemocrat.com.