Centrist Republicans and Democrats who favor a carbon tax see progressives' "Green New Deal" as a setback that will make it harder for them to broaden their base of support.

"It's unfortunate it might undermine the opportunity to do the right thing for the environment," said Rep. Francis Rooney of Florida, the Republican co-chair of the bipartisan Climate Solutions Caucus.

The Green New Deal resolution introduced last week is primarily a federal investment program with the goal of transforming the economy to reach 100 percent clean, renewable, and zero-emission electricity — achieving net-zero emissions — by 2030.

It does not mention a carbon tax, although it leaves the door open for it, since the resolution contains several nonbinding goals with no actual policies.

But progressives have quietly been moving away from carbon pricing as the best way to combat climate change in favor of government mandates.

Republicans who may have been open to carbon pricing could lose interest if progressives also oppose the policy, says former Rep. Ryan Costello of Pennsylvania, a centrist Republican who retired from Congress last year and who is now managing director of Americans for Carbon Dividends, a group that backs a carbon tax.

“The risk is the rollout has not created a political imperative for Republicans in Congress to offer an alternative,” Costello said of the Green New Deal. “If we think carbon pricing is what what provides a price signal to reduce carbon emissions, and the far left says 'we're not doing that,' a lot of center-right Republicans will look around and think if even progressives aren't there, why should I engage further on it?”

Former Rep. John Delaney of Maryland, a Democrat running for president in 2020, says the Green New Deal slows momentum for a carbon tax because of its extraneous focus on social and economic policy.

"I worry that saying to deal with climate change, we also need universal healthcare and guarantees jobs, that is making it harder to get something done on carbon pricing, which should be central to any strategy," Delaney said. "Just when we are putting together a coalition to actually get something done, people say we need to do something else. That doesn't make sense to me."

In December, Delaney co-sponsored the first bipartisan carbon tax bill to be introduced in nearly a decade. Rooney and Rep. Ted Deutch, D-Fla., reintroduced the bill last month, and it now has 12 other co-sponsors, all Democrats.

Delaney challenged his fellow Democratic nominees for president to support existing legislation such as the carbon tax bill, rather than the platitudes of the Green New Deal.

Several 2020 presidential contenders from the Senate have said they support the framework of the Green New Deal including Sens. Cory Booker of New Jersey, Kirsten Gillibrand of New York, Kamala Harris of California, Amy Klobuchar of Minnesota, and Elizabeth Warren of Massachusetts.

"The Democratic 2020 candidates who are not embracing the carbon tax structure and embracing the Green New Deal are basically saying I am not going to do anything on climate," Delaney said. "They care more about the talking point than the substance of getting it done."

Freshmen progressives like Rep. Alexandria Ocasio-Cortez, D-N.Y., however, argue carbon pricing wouldn't work on the grounds that oil and gas companies may not actually stop using fossil fuels just because they cost more.

Carbon pricing has struggled politically recently, encouraging the progressive opposition.

Democrats failed in 2009 to enact a cap and trade carbon pricing bill that passed the House but died in the Senate. That legislation would have set a limit on emissions while allowing companies to buy and sell allowances that let them emit a certain amount.

Green New Deal co-sponsor Sen. Ed Markey, D-Mass., one of the authors of the failed cap and trade bill, says the resolution does not prevent carbon pricing from being considered, but any plan must ensure that taxes don't go up for poor people.

Deutch' and Rooney's carbon tax bill tries to address that concern by distributing the revenue as a monthly rebate to American households, offsetting higher energy costs.

Low- and middle-income households would receive more in rebates than they pay in taxes, the bill’s authors say, while high-income households would pay more than they receive.

Supporters argue carbon pricing will become more popular as members begin to the debate particulars of the Green New Deal.

"The Green New Deal is sort of an aspirational resolution," said Sen. Chris Coons, D-Del., who introduced a similar carbon tax bill in December with former Sen. Jeff Flake, R-Ariz. "I do think putting a price on carbon will end up being a part of whatever the caucus-wide position ends up being."

Rooney and Costello view carbon pricing as the most realistic path for Republicans to support, because of its market-oriented focus on raising the price of carbon-intensive products, encouraging producers to switch to cleaner alternatives if doing so costs less than paying the tax.

"Republicans should really be putting their thinking hats on and saying a carbon tax is the most efficient, least regulatory, least big government way to price coal out of existence and start to lower the amount of carbon in our atmosphere, and warding off worse ideas like the Green New Deal," Rooney said. "It would help our standing with the American people to show our party can do something about climate change without having to go to socialism."

Yet, Costello and other carbon tax advocates say they can learn from the rollout of the attention-grabbing Green New Deal.

“The lead up to it and political imperative that was created among Democratic candidates to sign onto it is something that has proved very effective,” Costello said.

Former Rep. Carlos Curbelo, R-Fla., who introduced a different carbon tax bill last year before losing re-election in a left-leaning district, said proponents should sell the idea by talking about how the revenue could be used for productive purposes.

He noted that Green New Deal proponents emphasize the economic opportunities of reducing carbon emissions by encouraging infrastructure investment, creating clean energy jobs, and mitigating income inequality.

The carbon tax bill Curbelo introduced would have spent the revenues on infrastructure, along with flood-mitigation projects and other initiatives to protect against the effects climate change.

“Green New Deal proponents are focusing on the economic outcomes of their plan,” Curbelo said. “Certainly, those of us who support the idea of carbon pricing need to be equally creative. We can reduce carbon pollution and at the same time make investments in our country that can secure the future for generations.”