On Tuesday, two days after Elizabeth Warren announced her candidacy for president, an aide gave a statement to Axios that suggested the Massachusetts senator intends to court the green-leftist vote: “Senator Warren has been a longtime advocate of aggressively addressing climate change and shifting toward renewables, and supports the idea of a Green New Deal to ambitiously tackle our climate crisis, economic inequality, and racial injustice.”

But for some environmentalists, this rather anodyne statement was cause for concern, not celebration: She only supports the idea of a Green New Deal?

Those words are a worrying caveat, said RL Miller, political director of the super PAC Climate Hawks Vote, who noted that Warren hasn’t signed the Green New Deal’s pledge not to accept campaign donations from fossil fuel companies. “This will be our litmus test,” Miller said. “You don’t sign on to this, we don’t support you, period, full stop.”

Miller isn’t alone in her skepticism. Jack Clarke, the policy director at Mass Audubon, recently told E&E News that Warren “does not have a record of advocacy and leadership on climate change issues.” The news outlet surveyed the climate community about Warren’s record, and activists “struggled to name a climate issue on which the senator has made a name for herself.”

Make no mistake: Warren has a strong environmental record. She has near-perfect lifetime score from the League of Conservation Voters, and last year introduced a bill that would require public companies to disclose climate-related business risks. The fact that climate activists are hesitant to embrace the top progressives of the 2020 field shows how much the politics of climate change have shifted since 2016. The green vote matters more than ever—and it will be harder than ever to win it.