At this week's WGBH News debate between Gov. Charlie Baker and Democratic candidate Jay Gonzalez, the candidates differed on what may be the most pressing issue for environmentalists in this election — the expansion of the state's natural gas infrastructure.

Baker responded to a question about the issue by saying a study is underway to make sure the state's existing pipelines are safe.

"And I'm certainly not going to support doing anything with respect to any new pipeline until we actually get that study back and figure out what it tells us," Baker said.

But Baker didn’t say he's against more pipelines in the future. Gonzalez did.

"I will strongly oppose and do everything in my power to keep the expansion of natural gas pipeline infrastructure from happening," Gonzalez said.

The messages from the candidates have been consistent. Baker touts a record he says shows a commitment to the environment and to reducing pollution and the use of fossil fuels. Gonzalez says Baker hasn’t gone nearly far enough, and the climate crisis is going to require bold action.

But in this election, none of that may make any difference. Most voters don't list the environment as a top priority when polled. And for those who do prioritize it, Nathaniel Stinett, the founder of the Environmental Voter Project, said it may not come across during election time.

"By and large, environmentalists vote less often than the average American voter,” Stinett said. "And that's a real problem because politicians, believe it or not, don't really care what non-voters think."

During the 2016 presidential election, Stinett said 69 percent of registered voters went to the polls, but only 50 percent of environmentalists did.

The Environmental Voter Project uses a surprisingly accurate combination of polls and predictive models to determine who's most likely to identify climate change or the environment as one of their top priorities. And they can see from voter records which of those environmentalists are not showing up for elections. Then, the group targets them, and tries to get them to vote.

"Changing people's minds about climate and the environment is hard,” Stinett said. “In fact, it's darn near impossible. But finding people who are already with us and just tweaking their habits and turning them into better voters? Well, I won't claim that's easy. It's not. But it's a heck of a lot easier."

The Boston-based group is reaching out to voters in six states this election day, including Massachusetts.

"We're targeting 251,000 already-registered voters who deeply care about environmental issues in Massachusetts but are unlikely to vote this November," Stinett said.

That “targeting,” happens in the field by volunteers like Mary Cerulli. She goes door to door trying to connect with people on the Environmental Voter Project's list.

Recently in Jamaica Plain, Cerulli knocked on one door, and a woman answered whose husband is on the target list. She said he couldn’t come to the door because he was putting their baby to bed. So Cerulli explained why she was there.

"When folks are not consistent voters, their concerns aren't heard," Cerulli said, adding that the husband was inconsistent. The woman, who didn’t want to give her name so as not to shame her non-voting husband, asked for a flyer. She said she's now going to drag him to the polls.

"And I'll also ask him, 'What's that all about?'" she said about his voting record.

This is the kind of peer pressure the Environmental Voter Project is trying to capitalize on.

Cerulli's not new to canvassing. She's done it for Democratic candidates for years. And even though the Environmental Voter Project doesn't endorse candidates, in the Massachusetts gubernatorial election, she does have a personal preference.

"I'm for Jay,” she said, acknowledging that Gonzalez is the underdog in the race.

But the Environmental Voter Project isn't just focused on winning the next election. That's part of it, sure. But it’s really about changing the electorate. They want to get more environmentalists in the habit of voting. And when those people show up on rolls as consistent voters, they'll start getting calls from the candidate’s pollsters.

"And then they will be able to say I care about the environment,” Stinett said, “and that will get on the radar."

And if it's on the radar, the thought is, politicians will start to realize that in order to get elected, they're going to have to really focus on the environment.