Democratic leaders on Thursday tapped Rep. Kathy Castor (D-Fla.) to head a revived U.S. House panel on climate change , all but ending a dramatic monthlong effort to establish a select committee on a Green New Deal.

Castors appointment came as a surprise to proponents of a Green New Deal. The move also kicked off a controversy as the six-term congresswoman dismissed calls to bar members who accept money from fossil fuel companies from serving on the committee, arguing it would violate free speech rights.

Despite weeks of protests demanding House Democrats focus efforts next year on drafting a Green New Deal, the sort of sweeping economic policy that scientists say matches the scale of the climate crisis, Castor told E&E News the plan was not going to be our sole focus.

She then suggested that barring members who have accepted donations from the oil, gas and coal industries from serving on the committee could be unconstitutional.

I dont think you can do that under the First Amendment, really, she said.

That reasoning echoed arguments Exxon Mobil Corp. made in court as recently as this year to defend its funding of right-wing think tanks that deliberately produced misinformation about climate science to stymie government action on global warming.

Soon after the remarks were published, Castor walked back the statement in an interview with HuffPost, calling it an inartful answer.

But she said she did not know whether, as chairperson, she could bar members on the committee from serving if they accepted fossil fuel donations.

Maybe thats a discussion we need to have in the caucus, Castor said.

Its a stunning upset, essentially returning Democrats to the original plan leaders laid out before the protests began in November. The announcement comes as a loss for Rep.-elect Alexandria Ocasio-Cortez (D-N.Y.). Her meteoric rise and devoted base made it seem as if she were poised to win the burgeoning cadre of leftist Democrats a beachhead in a select committee that, even with limited capacity, would have demonstrated tangible power in Washington.

But, if its defeat, its bittersweet. The campaign, seemingly quixotic at first, shifted the stagnant climate policy debate not just to the left but, for the first time, in the direction of policies that could make a dent in surging global emissions and curb soaring income inequality. Coupled with back-to-back United Nations and federal reports that showed climate change already rapidly worsening, the effort established a new litmus test for lawmakers, breaking the binary of whether or not a politicians believes in the science of human-caused warming.

The movement gained stunning support in just a few weeks. A poll released Monday found 81 percent of registered voters supported the policies outlined under the Green New Deal resolution including 64 percent of Republicans and 57 percent of self-described conservative Republicans. Last Friday, more than 300 state and local officials voiced support for a Green New Deal in an open letter.

We dont have time to sit on our hands as our planet burns, Ocasio-Cortez said Thursday in a tweet . For young people, climate change is bigger than election or re-election. Its life or death.

Its unclear whether Ocasio-Cortez will even get a seat on the select committee.