The Hawaii Government Employees Association has endorsed U.S. Sen. Brian Schatz over U.S. Rep. Colleen Hanabusa in the Democratic primary for U.S. Senate, an early lift that could help propel his campaign.

The union’s board, meeting on Maui, agreed unanimously Friday to support Schatz after interviewing both Democrats. The union said Schatz is down-to-earth, expresses middle-class values, understands the challenges many working people have in raising young families, and vows to protect Social Security and Medicare.

Randy Perreira, the HGEA’s executive director, said the union believes both candidates are equally capable and friends of labor, but that Schatz empathized more with the issues working people are facing.

“For us, very difficult choice, but we feel that Brian is the choice that Hawaii should make for the future,” Perreira said.

The endorsement from the HGEA, the state’s largest public-sector labor union with more than 42,000 active and retired members, is the latest sign of traction for Schatz with organized labor.

The senator, who was appointed by Gov. Neil Abercrombie in December to replace the late U.S. Sen. Daniel Inouye, has won important labor endorsements from the University of Hawaii Professional Assembly, the State of Hawaii Organization of Police Officers, the Hawaii Building and Construction Trades Council, the Ironworkers Union Local 625 and other unions.

Hanabusa, who was a labor attorney before she entered politics, expects to draw significant support from the labor community. But labor endorsements have backed Schatz so far in the primary, clouding the idea that the congresswoman would be labor’s preferred choice.

Hanabusa’s campaign theme is that she has more leadership experience than Schatz and is better prepared to represent Hawaii in the Senate. The labor endorsements for Schatz, however, could undermine that premise among union members who are core Democratic primary voters.

“I think Brian clearly has the intelligence, the aptitude and certainly he has the commitment to Hawaii that will serve us well,” Perreira said. “And from all reports that we have from our international union (the American Federation of State, County and Municipal Employees), he has acquitted himself well so far in the Senate.”

Schatz thanked the HGEA for standing with him.

“This endorsement means a lot to me personally,” the senator said in a statement. “These are the people who provide critical public services every day, and they represent middle class across Hawaii. They represent clerks, nurses, researchers, cafeteria workers, school principals and many others. I will continue to fight for working families in the Senate.

“I thank HGEA for standing with me as we work to solve the challenges of our time, including protecting Social Security, creating jobs, growing tourism and expanding clean energy.”

Hanabusa said losing the HGEA endorsement would not change her commitment to working families.

“I am disappointed in the HGEA’s decision to endorse my opponent, given my long history of advocating on behalf of labor and workers,” the congresswoman said in a statement. “However, that does not change my commitment to continue supporting Hawaii’s working families. I will continue to work hard and reach out to win the support and vote of the rank and file who I have advocated on behalf of my entire career.”

Neal Milner, a University of Hawaii-Manoa professor emeritus of political science, said the importance of union endorsements can be exaggerated in political campaigns. The HGEA, for example, was one of many prominent labor unions to endorse former Honolulu Mayor Mufi Hannemann over Abercrombie in the Democratic primary for governor in 2010.

But Milner said he believes the HGEA’s endorsement of Schatz is important in this campaign because it comes at a time when both candidates are trying to establish themselves as the stronger option to succeed Inouye.

Inouye had wanted Abercrombie to appoint Hanabusa to replace him, and the congresswoman is counting on Inouye’s allies to help drive her campaign. But Milner said the HGEA’s endorsement sends a strong message that the party establishment footprint that often used to fall in behind Inouye will not do the same for Hanabusa.

“That pattern is not going to be the same,” he said.