Maine voters reject transmission line that would bring clean energy to Mass.

In what appears to be a stunning setback to Massachusetts’ climate goals, Maine voters on Tuesday rejected a referendum on a transmission line that would bring hydroelectric energy from Canada to the Bay State.

As of just before midnight, with 421 of the state’s 571 precincts reporting, a “yes” vote to stop the $1 billion project that is already under construction had garnered 60 percent support, according to unofficial results.

Energy from the line is a key part of how Massachusetts plans to achieve its goal of halving emissions by the end of the decade. The Maine vote does not spell the immediate end of the project, as the line’s supporters are already saying they will contest the referendum in court, but even that will likely result in a set-back to the project’s planned timeline—and there is no time to waste.

“We believe this referendum, funded by fossil fuel interests, is unconstitutional,” said Jonathan Breed, the executive director of a political action committee for the company behind the project, in an e-mailed statement. “With over 400 Maine jobs and our ability to meet our climate goals on the line, this fight will continue.”

Called the New England Clean Energy Connect, it would add 145 miles of new transmission line, connecting to the existing system in Lewiston, and upgrade another 50 miles of existing line. The project is the result of a deal among Hydro-Quebec, the state of Massachusetts, and Central Maine Power, a subsidiary of energy giant Avangrid. It was expected to start delivering energy to Massachusetts by December 2023.

The governors of Maine and Massachusetts endorsed the project, and US Energy Secretary Jennifer Granholm took the rare step last week of weighing in on a local ballot initiative, urging voters to support the transmission line.

Maine groups in opposition to the line have said it would cut through precious, untouched wilderness to benefit Massachusetts, with little net benefit for Maine. And while supporters of the line tout its climate bonafides, including that it would reduce carbon emissions equivalent to removing 700,000 cars from the road, reports commissioned by groups opposed to the line claim that the line would not actually have any climate benefit at all.

Environmental groups including the Acadia Center, a nonprofit promoting clean energy, support it, while others, such as the Sierra Club, have come out against it.

On Tuesday night, the Natural Resources Council of Maine, a key opponent of the transmission line, celebrated the win by calling on Central Maine Power to immediately stop work on the project.

“We also call on Massachusetts to honor this electoral outcome by selecting an alternative option for meeting its climate goals without imposing significant environmental harm on another New England state,” said Pete Didisheim, advocacy director of the Natural Resources Council of Maine, in an emailed statement.

It’s not just Massachusetts that was closely watching the vote. Across the country, scores of large-scale clean energy transmission projects are poised to be built, but experts say it is likely that other projects will run into resistance that’s similar to what happened in Maine.

In April, the advocacy group Clean Energy Grid published a report identifying 22 high-voltage transmission projects around the country that could begin construction soon, resulting in a 50-percent increase of national wind and solar generation. But, the group warns the success of those projects relies on timely financing and permitting, as well as federal regulators using their authority to break the “logjams that are preventing large regional and inter-regional lines” from being built.

So far, over 80 percent of the corridor has been cleared or widened, and 110 structures have been installed, according to Breed, of Avangrid’s political action committee, Clean Energy Matters.

The vote came after record-breaking political ad spending that left many confused and frustrated, making it possible for voters motivated by the climate to vote in opposite ways.

“From what I’ve seen, it’s not going to be that beneficial to Maine,” said Hobit Lafaye, after voting at her South Portland precinct to reject the transmission line. “Protect the climate by destroying our land? It doesn’t make any sense,” she said.

Standing outside the voting precinct at the Howard C. Reiche Community School on Portland’s West End, Ryan O’Neil, 42, said that after extensive research, he voted to allow the transmission line. When it comes to climate change, he said, “We can’t just do nothing.”

“It felt kind of like the goal of opposing the transmission line was really just NIMBY-ism,” O’Neil said. To him, the vote for climate was a vote to allow the transmission line to be built.

Sabrina Shankman can be reached at sabrina.shankman@globe.com. Follow her @shankman.