During Sunday night’s Democratic debate, Joe Biden did his best to convince voters he’d take the necessary steps to deal with climate change. He outlined the elements of his climate plan, promising to spend $1.7 trillion making the U.S. economy less destructive to the climate, ban new permits for oil and gas development on public lands and rally the world’s nations in an effort to protect the Amazon rainforest.

“All well and good,” replied Bernie Sanders. “But nowhere near enough.”

That describes the feelings of many climate activists these days towards Biden. If polls are correct that Biden will win Tuesday's primaries in a landslide, the former vice president will almost certainly become the Democratic nominee. That’s basically the worst possible outcome for the grassroots army that has helped make climate an important issue in this election. Many of its members severely distrust Biden because of his close links to the natural gas industry and his reported willingness to consider appointing people to his cabinet like JPMorgan Chase CEO Jamie Dimon, one of the world’s top financiers of fossil fuels.

But climate leaders contacted by VICE say the stakes of the 2020 election are too high for people to become despondent or withdrawn. “I don’t think we have the option of disengaging from the political process,” said Mitch Jones, a policy director for the group Food and Water Watch.

If Trump wins in the general election against Biden there is a serious likelihood of the world blowing past the best-case outcome on climate change. As VICE reported last month, experts fear another four years of fossil fuel expansion and diplomatic middle fingers to the rest of the world could spike U.S. emissions by 3.1 gigatons while encouraging other countries to drop out of the Paris agreement, obliterating any hope of stabilizing global temperature rise at the relatively safe threshold of 2 degrees Celsius.

“Biden’s plan is far from adequate and there is still a lot more room for him to meet the demands of science and our communities,” said Charlie Jiang, a climate campaigner with Greenpeace USA. “However, Biden’s plan is so far ahead of the dumpster fire that is the Trump administration and their active climate denial.”

That is not a super inspiring dynamic for the climate activists, campaign volunteers and primary voters who threw their support behind candidates like Sanders and Elizabeth Warren in hopes that a climate hawk in the White House would declare war on the fossil fuel industry and push Congress to implement an economy-transforming Green New Deal. With that no longer an option, leaders acknowledge there must be a shift in strategy. Instead of unifying behind a candidate, the movement plans to try to hold everyone accountable at once.

“I think what it requires of the grassroots environmental movement and the progressive wing of the environmental movement…is that we continue to pressure not only Joe Biden, not only Donald Trump, not only the Democratic and Republican Parties, but everyone in our political system,” Jones said. “Instead of disengaging, it requires doubling down.”

That could mean activists relentlessly confronting Biden on the campaign trail to make fighting the climate emergency his top priority—while at the same time working to get him elected. Groups like Food and Water Watch are also encouraging people to focus on all the candidates running for Congress or state legislatures in November. “Every time they have a fundraiser they’re met outside by protesters demanding they act,” Jones said. “Every time they have a town hall someone is there to press them on the issue. That’s how we’re going to keep this front and center.”

Biden is arguably susceptible to this type of pressure. When it was revealed last spring that he was considering a “middle ground” climate plan heavy on climate-destroying natural gas and fossil-fuel-perpetuating carbon capture and storage, groups such as the Sunrise Movement called it a “death sentence” and Greenpeace rated Biden’s approach a “D-”, the lowest of any Democratic candidate. Facing mounting attacks from the left, Biden shortly after released a $1.7 trillion climate plan committing the U.S. to net-zero emissions by 2050. “The movement of millions of people calling for a Green New Deal pressured him,” Jiang argued.

Greenpeace now ranks Biden a “B+” for promising to invest heavily in a job-creating clean energy technologies, phasing out subsidies for oil, coal and gas extraction, and once again making the U.S. a leading contributor to the Paris climate negotiations process. The group docked him marks for an emissions phase-out schedule not nearly as rapid as Sanders’ 2030 deadline. Biden, unlike Sanders, also refuses to support a nationwide ban on fracking for natural gas. He infamously told a young anti-fracking Sunrise protester in December that “you oughta vote for someone else.”

Biden’s campaign didn’t respond to VICE’s request for comment.

“His climate plan is still not nearly enough, but it’s an improvement from where he was,” Jiang said. “I would say Biden still needs to feel the pressure to stand with communities and not fossil fuel interests.”

Leah Stokes, a political scientist at the University of California, Santa Barbara, has also modified her opinion of Biden over the past year. Last May, she told VICE that “I don’t trust him at all…I think he’s got some explaining to do about what exactly his plan is to deal with the climate crisis.” But in a recent email she argued, “We need to win back the White House in November to see any real climate action federally. That's non-negotiable,” adding that, “I am cautiously optimistic that we can make Biden the climate champion we need. Because we must.”

Washington Post exit polls from Super Tuesday suggested climate voters are key to Biden’s support. He reportedly won 33 percent of people who rate climate a top priority, compared to 28 percent for Sanders. But experts speculated that many of these voters didn’t dig too deeply into the specifics of each candidate’s plan. “I’m not sure [voters] are capable of differentiating the degree to which the candidates are true climate hawks versus faux climate hawks,” George Mason University professor Edward Maibach told E&E News.

Part of the strategy for climate activists could mean making sure voters know precisely what about Biden's policies are insufficient. “The Biden plan has some areas that are weak or vague, such as on electricity decarbonization timelines and fossil fuel development,” said Stokes.

The grassroots climate movement will also attempt to make the case that its support for Biden during the general election hinges in part on him showing progress in these areas. “Biden could step up his game when it comes to taking on the fossil fuel industry,” Jiang said. “He could pledge to begin a full responsible phase-out of fossil fuel expansion. He could commit to rejecting permits for new fossil fuel infrastructure.”

Pushing for these commitments while also encouraging supporters and voters to help a-lesser of-two-evils candidate like Biden triumph against Trump isn’t the scenario many climate hawks and grassroots leaders hoped to find themselves in.

But time is running painfully short. Scientists just last week warned that the Amazon and other crucial ecosystems could be on the verge of a devastating and irreversible collapse due to climate change. “Our only option is to not wind down,” Jones said.

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