GOV. CHARLIE BAKER indicated he will be closely watching what happens in Maine on Tuesday, where voters will decide the fate of a ballot question that could block construction of a transmission line being built with money from Massachusetts electricity ratepayers to bring carbon-free hydro-electricity into New England.

“This is a big deal,” Baker said at a State House press conference on Monday.

The Baker administration is counting on the hydro-electricity to help achieve the governor’s zero net emissions target by 2050. Yet the power line running from the Quebec border to Lewiston, Maine, is facing pushback from Mainers resentful of Massachusetts’ attempted incursion into their state.

Baker raised concerns about the ballot question’s retroactivity. It would ban the construction of high-impact electric transmission lines in the Upper Kennebec region and require the Legislature to approve all other such projects anywhere in Maine, both retroactively to 2020, and to require the Legislature, retroactively to 2014, to approve by a two-thirds vote such projects using public land.

“A ballot question that retroactively denies an approval that was issued through a legal and appropriate process over a year ago and on which people have pursued and invested money in construction based on the approvals that they received sets a really difficult precedent,” Baker said.

Opponents of the project, however, say laws in Maine can be and have been applied retroactively in the past. They also note that Superior Court Judge Michaela Murphy in August ruled that the project as currently configured crosses a mile of state-owned land that wasn’t leased to the project in accordance with the Maine constitution, which requires a two-thirds vote of the Legislature. That decision is being appealed

Baker indicated the bottom line for him is dealing with climate change. “Truly electrifying big pieces of what is currently a fossil-fuel-based economy isn’t going to work if people aren’t willing to accept transmission capacity to make that happen. You can’t get from here to there without transmission capacity,” he said. “And I think that’s the reason why Paul LePage [the former governor of Maine] and Janet Mills [the current governor], people who don’t agree on very much, absolutely agree that this project should move forward.”

Baker also pointed out that the Biden administration is urging Mainers to voter no on the ballot question.

The project faces another hurdle as well. Importing the electricity into the New England power grid would require an upgrade of a circuit breaker at Seabrook Station in New Hampshire, but the owner of the nuclear power plant, NextEra, is balking at doing the work. NextEra, which is concerned the transmission line from Maine could hurt its business in New England, has provided funding in support of the Maine ballot question, indicating where its priorities lie.

The Seabrook issue is now before the Federal Regulatory Commission.