It said 2017 was a particularly extreme year , with Republicans in the Senate voting for environmental protections just 1 percent of the time. Forty-six Republican senators voted against environmental protections at every single opportunity.

Since Trump’s election, Democrats across Congress have voted for pro-environment legislation 92 percent of the time on average, compared with 5 percent for Republicans, according to an analysis by LCV.

Amid Trump’s zeal for environmental deregulation and an unfolding climate crisis that is now more divisive than abortion for many Americans, this polarization is at record levels.

The two main U.S. political parties regularly voted along the same lines on clean air and clean water provisions in the 1970s but started to diverge in the 1990s. They now occupy opposite ends of the spectrum, according to data collated by the nonpartisan group the League of Conservation Voters (LCV).

Donald Trump’s presidency has ushered in an era of unprecedented polarization between Republican and Democrat lawmakers when it comes to voting on measures to tackle the climate crisis, while the fossil fuel industry now almost entirely favors Republicans in campaign contributions.

“The average scores between parties used to be much closer with a lot of variation depending on regionalism,” said Sara Chieffo, vice-president of government affairs at LCV, which uses a panel of about 20 conservation organizations to score key votes on issues such as global heating, fossil fuel production on public lands, and wildlife conservation. “Now it’s hyper-partisan. From 2010 it really accelerated and now we see that the difference has really ballooned.”

As recently as George H.W. Bush’s presidency, Republicans in Congress were voting for environmental protections about one-third of the time on average. That support rapidly ebbed and has virtually vanished under Trump.

Meanwhile, Democrats, steered by a base that increasingly sees the climate crisis as an urgent priority, have become far more pro-environment in their voting.

The divide has been exacerbated by funding from the fossil fuel industry, which now firmly backs Republicans.

Data collected by the transparency group OpenSecrets shows donations from oil and gas interests were split relatively evenly between the parties until the 2000s. By the 2018 election cycle, 87 percent of industry contributions went to Republicans, with the proportion in the 2020 cycle, which is yet to be completed, reaching a record 89 percent.

Republican lawmakers once led environmental protection in the establishment of national parks and then landmark clean air and water laws in the 1970s, before the Ronald Reagan presidency began a fundamental shift, according to Naomi Oreskes, a historian of science at Harvard University.

“This was linked to a change in Republican thinking, inspired by Reagan, to see the federal government as ‘the problem’ and to roll back federal regulations in a range of domains,” Oreskes said. “Republican leaders in the U.S. do not merely prefer market-based solutions, they refuse even to acknowledge problems that cannot be solved by markets. Climate change is the case in point.”

Environmental groups have pointed to the influence of major energy companies, which knew about the dangers of the climate crisis for decades only to fund groups that spread misinformation and denial of the problem, while backing those who helped stymie action.

This has helped create an unusual level of denial about climate science among Republicans, compared with leading political parties in other democracies. “Behind closed doors politicians will tell you they believe in climate change, but they are terrified of saying that because they will get primary challenged for their position,” Chieffo said.

Polling has shown that younger Republicans are more willing to accept climate science, with many worrying about the climate crisis and the party’s unwillingness to address it.

“The Republican party has refused to accept the severity of most environmental issues, including climate change,” said Benji Backer, the president of the American Conservation Coalition, a group of conservatives who support action on the climate crisis. “Instead of being for different environmental policies, many in the GOP have solely become anti-every policy.”

Backer said Democrats and environmental groups were also to blame for the divide by supporting policies that “unnecessarily inflate the size of the U.S. government, don’t follow the science, and are focused on non-environmental issues.”

The Green New Deal, a resolution passed by progressive Democrats that calls for the rapid elimination of planet-warming gases as well as a jobs guarantee, has drawn particular ire from Republicans.

Chieffo said the division in Washington was in contrast to the growing public appetite for action on the climate crisis, as well as policies in ostensibly conservative states such as Idaho and South Carolina to bolster renewable energy.

“I think we are going to start seeing a greater diversity in voting and a move to sensibility,” she said. “We may well have hit rock bottom. But it’s really too soon to tell.”