Sen. Brownie Carson, D-Harpswell.

AUGUSTA, Maine — A proposal to study the emissions impact of Central Maine Power’s plan for a $1 billion hydropower corridor advanced procedurally after a vote in the Maine House of Representatives on Thursday, but not with enough support to take effect immediately.

The narrow vote was a rebuke to Gov. Janet Mills, a high-profile backer of the project who has been lobbying fellow Democrats on the issue. But it’s also a sign that she could find more than enough support to block this and other proposals aimed at the corridor using her veto power.

The proposal from Sen. Brownie Carson, D-Harpswell, is the first bill to go to the chamber floors aimed at the project, which would deliver Quebec hydropower to the regional grid through a 145-mile transmission line approved by the Maine Public Utilities Commission and awaiting further state permitting.

It passed the Democratic-led House in a 74-64 vote on Thursday. The study bill passed 30-4 in the Senate earlier this month and faces further action in both chambers. All but 18 Democrats voted for it in the House on Thursday. All Republicans except four — Patrick Corey of Windham, Randall Hall of Wilton, Dennis Keschl of Belgrade and Joshua Morris of Turner — opposed it.

It failed to win the two-thirds support needed in the House to take effect immediately on a future enactment vote. An “emergency” tag could be stripped by legislators to pass it with majorities, but it would take effect three months after the Legislature adjourns, likely next month. The House voted 87-50 to pass a version of the bill that provided funding for the study.

While it is still possible that proponents could win the required votes, Thursday’s vote endangers the timeframe in Carson’s proposal, which would direct the Maine Department of Environmental Protection to commission a study on the corridor’s effect on global carbon emissions by Aug. 15.

It aims to answer a key question of the debate around the corridor: whether it would reduce total emissions. A 2018 report found that it would reduce New England emissions by the annual equivalent of removing 767,000 cars from roads, though a study from opponents said the contract doesn’t guarantee that hydropower won’t be substituted for higher-emitting power.

Mills opposes the bill, but it’s unclear whether she will get the chance to veto it. The vote was a sign that her veto power may defend the project from legislative threats. Votes are pending on another bill from Rep. Seth Berry, D-Bowdoinham, that would require two-thirds of towns affected by the corridor to approve it at referendum or by vote of a municipal board.

For a roundup of Maine political news, click here to receive Daily Brief, Maine’s only newsletter on state politics via email on weekday mornings.

Michael Shepherd

Michael Shepherd joined the Bangor Daily News in 2015 after three years as a reporter at the Kennebec Journal. A Hallowell native who now lives in Augusta, he graduated from the University of Maine in...