BATH, Maine — Republican Sen. Susan Collins on Thursday received the endorsements of all four unions at Bath Iron Works in her bid for a fourth term representing Maine in the U.S. Senate.

According to Collins’ staff, this is the first time all four unions have made a joint campaign endorsement. It’s also significant because labor unions in Maine and nationally far more often ally themselves with Democratic Party candidates than Republicans.

Local S6 of the Machinists union, the largest union at Bath Iron Works with 3,400 members, endorsed Democratic gubernatorial candidate Mike Michaud, according to past president Dan Dowling.

Jay Wadleigh, current president of Local S6, said Thursday that he couldn’t remember the last time his union endorsed a Republican — in 2008 the union endorsed Collins’ challenger, Democrat Tom Allen. But Wadleigh said Collins’ “tireless” work on behalf of the company prompted the endorsement by Local S6, Local S7, the Bath Marine Draftsmen’s Association and the Independent Guards Association.

“Over the last five to six years, we’ve developed a closer and closer relationship with Sen. Collins, and it’s become more apparent the amount of work she does to keep contracts here, to help support a strong Navy, and to keep our members employed,” Wadleigh told the Bangor Daily News. “We’ve seen the work she did on the [DDG] 51 program, the [DDG] 1000 program, and as we’ve worked closer with her, we’ve found out about the midnight meetings with [Assistant Secretary of the Navy Sean] Stackley.”

Those meetings helped direct a steady flow of Navy work on destroyers to BIW during intense competition for Pentagon dollars.

Local S6 members voted to endorse Collins at their October 2013 meeting, according to Wadleigh. That meeting occurred four days before Collins’ opponent, Democrat Shenna Bellows, launched her Senate campaign.

While some union members did not support the early endorsement of Collins, “the majority of the membership feels strongly that she does work hard for us,” Wadleigh said.

Wadleigh said the union’s national leadership allows S6 autonomy to endorse who they choose.

Beverly Harris, president of the 639-member Bath Marine Draftsmen’s Association, said Local 3999 received no objection from the national office of the International Union, United Automobile, Aerospace and Agricultural Implement Workers of America.

“The UAW understands what Sen. Collins does for our membership,” she said, adding that while her union has endorsed Republicans in the past, it has not done so in at least the past nine years.

Collins was on hand Thursday at the Local S6 headquarters across from the Bath shipyard to receive the endorsement in person.

Announcing the endorsement of the Independent Guards Association, president Nate Doherty said, “She cares about this yard … She’s affectionately called this place her yard, and we say that right back to her, ‘You’re our senator.’”

Noting that BIW was her first stop the day after her re-election in 2008, Collins said, “I pledge to you that I will always work hard to do what is best for BIW, our state and our country.”

Reached Thursday afternoon, Bellows said despite the early endorsement of Collins by Local S6, “I am confident that I will have the support of the shipyard workers, just as I have the support of more than 10,000 workers, from some of the largest unions across the state including plumbers and iron workers. Throughout the state, the largest unions are standing up to support my candidacy because of my background and my values.”

Bellows continued, “There’s something wrong with a system that has brought us to a place with record high profits for General Dynamics and such a significant loss of jobs over the last two decades. The profits of General Dynamics, which owns the yard, are at a record high, but the number of people employed at the shipyard is thousands less than it was 18 years ago.”

Jay Korman, senior Navy analyst with the Washington, D.C.-based consulting firm The Avascent Group, said Thursday that the unions’ endorsement is a reflection of Collins’ hard work for Maine jobs.

“Collins is one of the few people who can still bring together coalitions of support, and that’s not as easy as it used to be,” Korman told the Bangor Daily News. “Those people are few and far between. When you look at the bottom line, and the work General Dynamics has done, she’s done a great job … as long as you’re looking out for the yard, it’s hard to vote against you.”