Victor Ouimette, Brad Matson and Karl Krall all defeated incumbent board members in Tuesday's elections, the Milwaukee Journal Sentinel reported Wednesday.
Ouimette, Matson and Krall were among seven candidates the group Americans for Prosperity branded as opposing Gogebic Taconite's plans for a 4½-mile-long iron mine in the Penokee Hills near Mellen in far northern Wisconsin.
The project has become one of the most contentious environmental issues Wisconsin has faced in years; Gogebic Taconite has promised the mine will create hundreds of jobs for the economically depressed region, but conservationists fear the project will pollute the area's waters. The Bad River Band of Lake Superior, whose reservation lies just north of the site, is especially concerned that mine pollution will destroy its wild rice beds.
Republican lawmakers passed a law relaxing the state's mining regulations last year to help jump-start the project, angering mining opponents even further.
The county supervisors' stances are crucial as the company enters into negotiations with the board over zoning regulations for the project.
Americans for Prosperity circulated two full-color mailings in recent weeks aimed at getting supervisors who support the mine elected. One mailing criticized the candidates the group identified as mine opponents. The other mailing backed mine supporters. Four of those mine supporters won Tuesday.
Krall told the Wisconsin State Journal last month he actually supports the mine. Ouimette told Wisconsin Public Radio last month that he, too, backs the project.
Americans for Prosperity has become a prominent political force by spending heavily on races independent of candidates. The group spent $1.4 million against Democratic U.S. Senate candidate Tammy Baldwin in 2012, the newspaper reported. Baldwin went on to defeat former GOP Gov. Tommy Thompson.