The Kennebec River is seen alongside Route 201 in Caratunk in this Aug. 20, 2020, file photo. Credit: Natalie Williams / BDN

AUGUSTA, Maine — A collective $20.6 million was spent by backers of Central Maine Power’s controversial proposed $1 billion hydropower corridor through the end of September, some of that long after the state’s high court deemed an anti-corridor referendum unconstitutional.

Clean Energy Matters, the political committee backed by CMP and its parent company Avangrid, spent $12.3 million through the end of September, according to reports filed with the Maine Ethics Commission. Another committee financed by its partner in the project, the provincial-owned Hydro-Quebec, which would supply the power, spent about $8.3 million.

The effort did not go to the ballot but still was the most expensive referendum in Maine’s history. It is likely the spending will continue: there are two new referendum bids from CMP skeptics that have been filed with Secretary of State Matt Dunlap’s office and are undergoing review.

One would pressure the Legislature to use existing power to block the corridor from being built, while another looks to buy out CMP and Versant Power to create a controversial consumer-owned utility.

Both companies continued to spend after the referendum question was defeated, documents show, with nearly half of Clean Energy Matters’ spending from Aug. 19 to Sept. 30 devoted to a $489,000 media buy. Hydro-Quebec continued spending “awareness campaigns” and strategy.

Hydro-Quebec also paid a consulting agency about $41,000 to conduct additional polling around the project in late August, according to disclosures made by the consultant through the U.S. Foreign Agents Registration Act.

Corridor opponents spent relatively little in comparison. Mainers For Local Power, which is primarily funded by two-Texas based natural gas companies, Vistra Energy Corp. and Calpine Corp., spent a collective $2.2 million through the end of September, according to filings. No CMP Corridor, a grassroots group that led the ballot initiative campaign, spent nearly $200,000.