With Super Tuesday’s primary returns and caucus results now tallied, commentators are declaring that Bernie Sanders faces a tougher path to victory than ever. But even if the Vermont senator does not become the nominee this summer, his campaign, combined with the efforts of environmental groups such as 350.org, Sierra Club and Greenpeace, has already had an enormous impact on the conversation Democrats are having around climate.

Last spring, Hillary Clinton launched her campaign with a fairly strong environmental platform — especially compared with past Democrats who won the nomination. Shortly afterward, Bernie Sanders rolled out a far more aggressive agenda, including bans on fossil fuel extraction on public lands and via offshore drilling, and a complete ban on fracking. Sure, his plan was impractical, given a likely Republican Congress, but it drew the battle lines.

“In 2008, we were lucky to hear about climate change at all,” says Cassady Sharp, a spokesperson for Greenpeace’s democracy campaign. “And now we have Democratic candidates — and when Martin O’Malley was in the race this was true too — basically fighting over who has the better climate plan.”

It makes sense for candidates to take bold stands; climate is one of the top issues millennials care about, and polling indicated it was a factor in the Iowa caucus. The urgency of climate change and the need to address it has become alarmingly evident over the last several years, and with the economic concerns of the financial crisis playing a less central role than they did in 2008, voters are demanding climate action.

Sanders’s longtime focus on both climate change and the big-money influences that have slowed America’s response to it have won him the support of many strong climate advocates. The super PAC Climate Hawks Vote has ranked Sanders in the top 10 percent of senators on the environment every year since they started ranking senators in 2011, and ranked him the top senator in the 113th Congress. “With Bernie you can see his recent record in the Senate, he’s pretty strong,” says Sharp. Friends of the Earth endorsed Sanders last summer, and high-profile environmental activists like Bill McKibben and Naomi Klein have written favorably of his campaign. “Gentle reminder: the climate decisions in the next 5 years will shape the future of humanity. Hillary cannot be trusted. Vote #BernieSanders,” Klein tweeted before Super Tuesday.

Perhaps more importantly, Sanders’s policy platform has given activists who care about climate change a goalpost to steer Clinton toward. And it’s been working. Though Clinton at first equivocated on opposing the Keystone Pipeline and Arctic drilling, she came out against both before the Obama administration took a clear stand. Last October, she announced her opposition to the Trans-Pacific Partnership, a trade agreement that the Obama administration supports but that environmentalists worry would lead to a spate of lawsuits by corporations seeking to strike down environmental regulations that hurt their business.

Environmental groups are continuing to push Clinton further, with activists popping up at campaign stops, cellphone cameras rolling, ready to get her on the record. When, on Feb. 4, one New Hampshire activist asked, “Would you ban the extraction of oil, gas and coal on public lands?” Clinton immediately replied, “That’s a done deal.” It was a stance she hadn’t taken before.

And when, last Thursday, at a South Carolina rally, Carolina Arias, a University of North Carolina student, asked whether Clinton would “make sure we do not support trade deals that exacerbate climate change,” Clinton indicated that her priority would be strengthening the Paris accords, not renegotiating the Trans-Pacific Partnership, which she has already condemned, or pushing the similar Trans-Atlantic Trade and Investment Partnership, which she has not.

“We really need to put our efforts into enforcing and carrying out the Paris climate deal,” Clinton told the crowd, “because that gives us the best chance to bring the world around before it’s too late.”

“Every time somebody provokes her on the campaign trail she seems to get stronger and stronger,” says Greenpeace’s Sharp. Jason Kowalski, a spokesman for 350 Action, which conducts bootcamps to train activists on how to get candidates on the record, agrees that momentum is moving in activists’ direction. “This is our moment, when we are much stronger than the fossil-fuel industry,” Kowalski told Bloomberg. “Once these decisions go behind closed doors, the lawyers and the lobbyists of the oil industry will outpower us.”

Environmental groups want Clinton to reject dirty energy money starting now, before the general election. According to a Greenpeace tally, Clinton has so far accepted $126,200 from 53 oil and gas industry lobbyists, and 11 lobbyists connected to the industry have bundled more than $1 million in contributions to her campaign. (The industry has thrown many times that much at the Republican primary contests.) She also left the campaign trail to attend a fundraiser with a group invested in offshore drilling and fracking operations shortly before the Iowa Caucus. The optics were not great — she was criticized for the decision — and the Sanders campaign used the episode for its own fundraising.

Last month, as Nevada was gearing up for its Democratic caucuses, Greenpeace flew a “thermal airship” over the Las Vegas strip. Similar to a hot-air balloon, the airship was able to hover over the city for several hours before the wind picked up. The message on its side: Hillary: Say No to Fossil Fuel $$$.

“We heard from some people working on her campaign that they were nervous we’d do it again,” says Greenpeace’s Sharp. “So we’ll definitely be doing it again.” Activists say they hope to next get Clinton to sign a pledge not to accept money from fossil fuel interests, and to go on the record against fracking. Sanders has already done both.

In fact, some of Sanders’s Super Tuesday wins might be partly due to his position on fracking. Oklahoma, where he won 52 percent of the vote, has been rocked by increasingly violent earthquakes in recent years, a phenomenon connected to the fracking boom in the state. Colorado, another state where Sanders triumphed, has also seen an explosion in oil and gas industry activity. Sanders is even leading Clinton in coal country, in spite of his strong climate positions.

Other states that are ground zero in various environmental battles head to the polls in the next few weeks: Ohio, which has also been rocked by fracking-related earthquakes, votes on March 15; Washington state, where voters are fighting against facilities to ship fossil fuels to market, votes on March 26.

So the Democratic frontrunner might evolve a good deal more on climate before the general election.