Durham, New Hampshire—The winning campaign in New Hampshire? That’s easy. It’s the drive led by groups such as the Sunrise Movement to make the climate crisis an issue in the 2020 presidential race.

While the Democratic National Committee continues to refuse to organize a candidate debate on climate issues, the candidates themselves have taken those issues onto the campaign trail in this first-primary state. And it is proving to be every bit as politically potent as activists such as 350.org founder Bill McKibben have long argued that it can and must be.

“For three decades in American politics, climate change has been the issue that wasn’t. Even as the temperature steadily rose, and evidence mounted that it was human behavior—and human policies—that were driving this change, candidates mostly deflected. And it wasn’t hard: During the 2016 general election, no journalist even asked the presidential candidates a debate question on the topic,” says McKibben. “But that’s not the case this time. Climate change matters for Democratic voters.”

Advocates often argue hopefully that the moment has come for their issues. But the proof is in the focus of the campaigns and the response. This equation is central to the closing push by Vermont Senator Bernie Sanders, the front-runner in most polls of likely voters in today’s Democratic primary.

At mass rallies—including a huge one Monday night on the University of New Hampshire campus that featured US Representative Alexandria Ocasio-Cortez, the New York Democrat who has championed the Green New Deal—Sanders has brought fierce urgency to his appeals on the issue.

Proposing a new approach to foreign policy that focuses on saving the planet, the senator told a crowd of almost 2,000 supporters that had packed a sports arena in Keene Sunday night, “Maybe, just maybe, instead of spending $1.8 trillion a year collectively on weapons of destruction designed to kill each other, maybe we pool our resources and fight our common enemy, which is climate change.”

The crowd erupted in the loudest applause and the longest show of enthusiasm on a very enthusiastic night. Sanders has been talking about climate issues for decades, but this year he has turned the volume up. It’s a core component of his outreach to the young voters who have been critical to his coalition. When the muddled Iowa Caucus results were finally announced—showing a 6,000 popular-vote win for Sanders, along with a narrow delegate equivalent advantage for former South Bend mayor Pete Buttigieg—the Sunrise Movement credited young climate activists with giving Sanders essential support.

“Young people across Iowa turned out in historic numbers to show that our generation is the largest political force in this nation,” said Sunrise Movement cofounder Varshini Prakash. “Our movement and our Iowa team quite literally shifted public opinion on the climate crisis—bringing Iowan public support for the Green New Deal to an unprecedented majority and helping to push Green New Deal champion Bernie Sanders to the top of the race. If this many young people participated in the notoriously inaccessible and time-intensive Iowa caucuses, this could be a promising sign for even higher youth turnout in New Hampshire and on Super Tuesday to bring Sanders more victories.”

The Sunrise Movement, which has endorsed Sanders, is making a major push for him in New Hampshire—knocking on doors and logging thousands of calls for the senator.

But Sanders is not alone when it comes to talking about the climate crisis. Massachusetts Senator Elizabeth Warren is highlighting her detailed plan to address the issue. Minnesota Senator Amy Klobuchar says, “As President, I will lead and tackle the climate crisis starting on Day One.” Even former vice president Joe Biden is talking about the issue, after facing pressure from climate activists who challenged him at New Hampshire events last fall.

Tom Steyer, the billionaire who has poured resources into organizing around climate issues, is running ads featuring veteran New Hampshire elected official and environmental activist Dudley Dudley. Dudley, a well-regarded progressive with deep roots in the state, says, “Our seas are rising, our forests are burning, and Tom is the best candidate to tackle those issues and beat Donald Trump in 2020.”

Dudley makes the point that beating Trump is a necessary step when it comes to addressing the crisis. The president, who rallied supporters in Manchester on Monday night, has pulled the United States out of international efforts to address climate change and empowered the fossil fuel industry at home.

New Hampshire State Senator Jeanne Dietsch, a Democrat from Peterborough, says Trump’s record will hurt him in November. “New Hampshire is a very environmentally conscious state. There are even Republicans who are environmentalists.”

Probably not enough of them to give a major boost to the president’s most serious Republican primary rival, former Massachusetts governor Bill Weld, but Weld was reminding voters of the environmentalist legacy of New England Republicans and telling small crowds, “We have to believe in science.”

Arguing that the Republicans must reject not just Trump but climate denialism as well, Weld says, “We’ve got choices about what kind of Republican Party we want going forward, and I hope we don’t choose the know-nothing party.”