Joe Manchin announced his first Senate campaign in 2010 with an ad showing him taking a shot at the Democrats’ cap-and-trade bill with a rifle. It proved to be a metaphor for his time in Congress. 

During the 13 years the Democrat represented the people of West Virginia in the upper chamber, he proved to be an essential supporter of climate legislation even as he stood in the way of climate legislation. He had no qualms about withholding votes on key legislation like the Build Back Better Act or demanding concessions — often in support of fossil fuels — to support party priorities like the landmark Inflation Reduction Act passed in 2022. In a closely divided Senate, his ability to stymie President Joe Biden’s agenda made him a fickle ally in the climate fight — but an ally just the same.

And now he’s quitting.

Manchin, 76, was gearing up for his third Senate run and was widely expected to face Jim Justice, West Virginia’s Republican governor and a billionaire coal operator. He was looking at a tough race but earlier this year defiantly declared, “Make no mistake. I will win any race I enter.”

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Apparently, he’s had second thoughts. Manchin announced on Thursday that he believes in his “heart of hearts” that he has “accomplished what I set out to do for West Virginia” and will not run after all. He didn’t say what he might do next, but said he is leaving Congress in favor of a “movement to mobilize the middle and bring Americans together.”

Some have speculated that Manchin may be on the cusp of a third-party presidential run, which would, yet again, make him a thorn in Biden’s side — a particular strength of his. Regardless, his departure likely ensures a stronger Republican presence in the Senate, if not a GOP takeover of the chamber, and will make passing any kind of climate legislation a whole lot harder.

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“I would think the implications are straightforward for climate policy,” Robert Stavins, a professor of energy and economic development at Harvard University, told Grist in an email. “If Manchin is (surprisingly) replaced by another Democrat, that could have positive implications for federal climate policy. If he is replaced (as seems likely) by a Republican, then the implications will be decidedly negative, particularly if it means a change of the Senate majority party.” 

Not that Manchin ever made passing any kind of climate legislation easy. He is socially conservative and a big supporter of coal, both because of where he comes from and because his family owns a coal processing plant that earns him $600,000 per year

Since arriving in Washington in 2010, he has rejected efforts to cap carbon emissions, opposed the Clean Power Plan, and supported building a petrochemical hub in the Ohio River Valley. He also voted with President Donald Trump about 50 percent of the time. But Manchin, being Manchin, also endorsed wind energy in his home state, came out against mountaintop-removal coal mining, and worked with the United Mine Workers Association to help protect miners from black lung disease. 

Biden took office in 2021 with Democrats holding a one-seat advantage in the Senate. That gave Manchin outsized power to influence the president’s agenda, as he was often the deciding vote. He refused to sign on to a little-known but vital piece of legislation, called the Clean Energy Performance Program, that would push the nation toward renewables even after multiple changes, and infamously refused, at the last minute, to support Build Back Better, even if it did ultimately pass.

However, as Democrats will grit their teeth and admit, what climate legislation did pass during Biden’s presidency did so largely because of Manchin’s support. He has played a role in the passage of several large climate bills and cosponsored the Energy Act of 2020, aimed at lowering greenhouse gas emissions, which passed as part of the year’s omnibus spending bill. And he did get the IRA passed, ushering in the nation’s first sweeping effort to address climate change.

Still, Manchin made his support of Biden’s signature legislation contingent upon Democratic approval of a permitting reform bill. Although he framed it as a means of accelerating clean energy projects, environmental groups noted that it also cleared the path for fossil fuel projects, including the Mountain Valley Pipeline that will carry natural gas 304 miles across West Virginia to Virginia. Manchin boasted in September that “because of the IRA, we are now producing fossil fuels at record levels.” He also was quick to remind voters in the bright-red Mountain State that the law was a bipartisan victory. “The Inflation Reduction Act isn’t a red bill or a blue bill, and it sure isn’t a green bill,” he said. “It’s an American bill.”

Still, his popularity at home took a hit. Barry Rabe, a professor of public policy at the University of Michigan, believes Manchin genuinely thought his support of the IRA would play better among his constituents. “I think he was kind of taken aback by the backlash that he received. The IRA is massive and throws a lot of money in different directions,” Rabe said. “He had every expectation [that] a lot of that would end up in West Virginia.” 

But Manchin’s once reliably blue state has changed during his time in Congress. The socially conservative, labor-friendly Democrats who used to run things there are a vanishing breed, replaced by Republicans at every level. Despite Manchin’s efforts to appeal to the middle, Eric Engle, the board president of the Mid-Ohio Valley Climate Action, says voters are increasingly partisan. A successful Democratic candidate must offer a genuine alternative to Republicans rather than try to appeal to everyone with the occasional bipartisan gesture. Otherwise, voters are likely to lean toward Jim Justice — and the GOP knows it. 

“We like our odds in West Virginia,” Republican Senator Steve Daines, who chairs the National Republican Senatorial Committee, said in a statement

The sole Democrat left in the Senate race is Zach Shrewsbury, a Marine Corps veteran and coal miner’s grandson who is running as a worker-friendly candidate. He is a relative unknown, while Justice, who has been endorsed by Trump, is immensely popular, despite his history of business mismanagement and refusal to address his companies’ dangerous unreclaimed coal mines.

Justice is widely expected to win the Republican primary in February. Should he make it to Congress, Engle says Justice won’t be any help addressing climate change. His record as governor and a businessman shows he is no friend of environmental regulations.

“Justice has never seen a bill or a lawsuit or a liability that he didn’t try to weasel his way out of,” Engle said. “He’s trying to use being in political office to dodge accountability, and to maybe change rules and regulations as they apply to him.” 

Nationally, political analysts say Manchin’s decision may not change much given that public opinion was already tilting against him. But with Manchin out, Republican and Democratic organizations probably won’t pay much attention to the state and instead focus on contested races in places like Ohio and Florida.

Rabe looked even further down the road, to what the U.S. and West Virginia might look like not just after Manchin, but after whoever comes after him. His efforts to play both sides — sometimes supporting climate policies while sometimes supporting fossil fuels — probably won’t play any longer. That could force the state’s Democrats to embrace something other than the middle-of-the-road energy and environmental policies Manchin, and other representatives of fossil fuel-producing states, have embraced for so long.

Correction: An earlier version of this story misidentified Joe Manchin as the Democratic senate majority leader.