Heavy machinery is used to cut trees to widen an existing Central Maine Power power line corridor to make way for new utility poles, Monday, April 26, 2021, near Bingham. Credit: Robert F. Bukaty / AP

AUGUSTA, Maine — Total political spending in the fight over the Central Maine Power Co. corridor topped $60 million at September’s end as energy companies on both sides continued to throw cash at the Nov. 2 referendum seeking to kill the project.

The upcoming ballot question aims to empower the Legislature to revoke a lease for a portion of the 145-mile transmission line that aims to bring hydropower from Canada to connect with the New England energy grid near Lewiston. It is corridor opponents’ second attempt at a referendum after a previous ballot initiative was declared unconstitutional last year.

Since late 2019, energy companies have poured at least $64 million into the fight, according to campaign finance filings submitted Tuesday. That includes both direct and in-kind contributions to several political committees and other groups. Pro-corridor groups have outspent opponents, though an anti-corridor group made its biggest investment yet this quarter.

It is a record for spending on a referendum in Maine and the all-time second-most expensive political campaign in the state’s history, trailing only the 2020 U.S. Senate race.

The spending was once again led by CMP, which poured another $8.6 million into its political committees in the past three months, according to a campaign finance report filed Tuesday. Hydro Quebec, the Canadian energy company that would supply hydropower for the corridor, poured another $4.9 million into its political committee in the third quarter of 2021.

The group has spent more than $14 million since fall 2019. Maine lawmakers targeted the company, which is owned by the province of Quebec, earlier this year with a bill aiming to block ballot question spending by entities affiliated with foreign governments. Gov. Janet Mills, a Democrat, vetoed the measure and proponents want to pass it by referendum in 2022.

On the anti-corridor side, NextEra, a Florida-based company, donated another $7 million to a ballot question committee called Mainers for Local Power, a significant increase in investment compared to the $1.6 million it gave last quarter. Despite its name, the group was founded by two other energy companies, Calpine and Vistra, and the three have accounted for nearly all of its fundraising. All stand to lose shares of the regional power market if the corridor is built.

Mainers for Local Power also contributed $150,000 to No CMP Corridor, accounting for most of the group’s funding. Advocates with No CMP Corridor have been the faces of the anti-corridor campaign, including tabling at agricultural fairs in the past few months. Significant funds continue to flow between groups. No CMP Corridor also donated $140,000 to Say NO to NECEC, a nonprofit opposing the corridor that does not have to disclose donors or spending.

Early polling has suggested corridor opponents have an advantage going into Election Day, with 50 percent of those surveyed saying they disapproved of the project in a Spectrum News/Ipsos poll last month, while only 34 percent supported it. The issue has not fallen along typical political lines, with business and labor groups backing the corridor against grassroots opposition.

Environmental groups are split on the issue, with some touting the clean energy benefits of hydropower, which would help reduce the use of coal-powered electricity in New England in the short-term, while others have decried the negative effects of construction in western Maine and argued that the state should focus on other renewable energy sources.

The well-funded political groups on both sides have flooded the airwaves in recent weeks with ads attempting to sway voters, with CMP allies focusing their messaging on the potential consequences of the referendum for other projects and Maine’s overall business climate, while corridor opponents highlighting the trees cut down during the construction process.