A sign protesting the proposed Central Maine Power corridor is seen on a mailbox on the side of a road in The Forks on Aug. 20. Credit: Natalie Williams / BDN

Maine’s campaign finance watchdog can request financial records from a dark-money group opposing Central Maine Power’s proposed $1 billion corridor project as part of a broader investigation, a judge ruled on Monday in state court.

Stop the Corridor sued the Maine Ethics Commission in June aiming to shield its donors from public view after the commission voted to require the group to disclose financial information to the commission as part of an investigation into whether Stop the Corridor had to register as a political committee after it gave $85,000 to another anti-corridor group.

But Cumberland County Superior Court Justice Thomas Warren disagreed with the anti-corridor group’s argument that the state agency had no jurisdiction to do so, denying a delay of the ethics commission’s order by finding the group was unlikely to succeed and that the information requested was relevant to the Ethics Commission’s investigation.

The lawsuit was born out of an ethics complaint from Clean Energy Matters, a CMP-funded political action committee, when the corridor was threatened by a referendum question since deemed unconstitutional by Maine’s high court. Opponents are now gathering signatures for another referendum aimed at blocking the $1 billion project by legislative means.

Stop the Corridor opposed the investigation, which would require it to reveal donors to the commission even as Maine Ethics Commission staff have insisted that such information would be kept private during the investigation. Representatives have said the group is looking to influence the corridor’s fate through the permitting process and not the ballot box.

The commission denied a request from the group to halt a subpoena in October. If the commission ruled that it is a political action committee by itself, the group would have to register and report its donors.

The wrangling over the corridor has already amounted to one of the biggest campaigns in Maine history. Before the first referendum was invalidated in August, CMP and its affiliates spent $17 million to boost the project. Since then, groups on both sides have spent $3.7 million, including out-of-state generators opposed to the project that would cost them regional market share.