There’s just one wrinkle: There’s not a single, official Green New Deal. Much like “Medicare for All,” “Green New Deal” refers more to a few shared goals than to a completed legislative package. (The original New Deal basically worked the same way.) Now a number of environmental groups are trying to make those goals more specific. But they’re running into a snag: The bogeymen that haunted old progressive climate policies are suddenly back again. And the fights aren’t just about nuclear power.

Late last week, more than 600 environmental groups published a letter laying out an environmental agenda for the new Congress. The groups did not explicitly describe a Green New Deal, but their sought-after legislative program looked and quacked a lot like one. They demanded an all-renewable power grid, an end to fossil-fuel exports, and a ban on gas-powered cars by 2040. “If we are to keep global warming below 1.5 degrees Celsius, we must act aggressively and quickly,” the letter said.

Of the hundreds of groups that issued the demands, one stood out: the Sunrise Movement, a new, youth-led activism corps that flung the Green New Deal into national prominence last year. More established organizations—including Friends of the Earth, 350.org, and the Center for Biological Diversity—also signed.

The letter seemed like the standard collection of progressive climate goals, but on closer inspection it veered into new and controversial territory, especially in the places where the groups said what they would not support. They promised to “vigorously oppose” any legislation that promoted nuclear power, hydroelectric power, and carbon capture and storage, a still-experimental technology that could remove carbon dioxide directly from the atmosphere. They also forbade Congress to use any “market-based mechanism” to administer climate policy.

The absolute nature of these demands reportedly kept a number of established green nonprofits—including the Sierra Club, the Audubon Society, and the Environmental Defense Fund—from signing the letter. And the Sunrise Movement has backed off the letter somewhat. Stephen O’Hanlon, a spokesman for the group, told me that the letter to Congress is “not the full vision of the Green New Deal. It is a set of climate priorities for the new Congress.”

But the demands point to a broader shift for Sunrise—particularly around the issue of carbon capture and storage. In November, when Sunrise first demanded that Nancy Pelosi create a Green New Deal committee, it said that any potential plan must fund “massive investment in the drawdown and capture of greenhouse gases.” Sunrise seemed, in other words, to endorse carbon-capture research.

But the final version of that same document omits capture at all: It calls only for investment in the “drawdown of greenhouse gases.” This change has not been previously reported, and it appears to have been made quietly. Greg Carlock, who developed a different Green New Deal plan for the left-wing think tank Data for Progress, told me he was not aware of the change.