Story highlights Unions representing steelworkers and letter carriers are signing on to a new group

Quarterly filings are due with the Federal Election Commission on Saturday

Washington (CNN) Seven labor groups have joined forces with a Democratic super PAC trying to pool their party's field programs, an effort that the group claims has now raised $60 million.

For Our Future, a new outside group set on avoiding duplication among traditional powerplayers on the left, will report this weekend having collected millions from a new corps of donors, including unions representing steelworkers and letter carriers, the group told CNN Friday. Yet the biggest supporter remains Tom Steyer, the billionaire climate activist who was the Democratic Party's top donor during the 2014 cycle.

Steyer has given $20 million to the organization through his personalized super PAC, NextGen Climate, and said in an interview Thursday that he did not plan to increase the size of that commitment in the coming weeks. Other top givers to the super PAC are Dustin Moskovitz, the Facebook co-founder who has stunned Democrats by injecting groups with $35 million out of nowhere, and his wife who together donated $5 million to For Our Future.

"The organization is basically in place," Steyer said. "If we decided at this point, 'Let's go do Hawaii', you really can't."

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