WASHINGTON — U.S. Democratic Sen. Joe Manchin III announced Thursday he does not plan to run for reelection come 2024, giving Republicans an opportunity to pick up a seat and increasing their chances of flipping Senate control.

A centrist who has long frustrated his party’s leadership and outside advocacy groups with his views on fossil fuel production, gun control and abortion rights, among others, Manchin nonetheless helped Democrats win their 51-49 Senate majority and steer the chamber’s agenda. His retirement will make the task of keeping that majority immeasurably more difficult.

Senate Republicans only need to win two seats to gain a full majority, if they can retain all 11 of their current seats in the 2024 election. Democrats and Republicans could also end up with a 50-50 split again.

National Republican Senatorial Committee Chair Steve Daines, a Montana senator, indicated in a written statement that Manchin’s retirement could benefit the GOP.

“We like our odds in West Virginia,” Daines said.

West Virginia Republican Gov. Jim Justice and U.S. Rep. Alex Mooney are competing in the GOP primary.

Democrats to have any chance of a win may need to recruit a strong candidate to run for the seat that Manchin is vacating, though their bench isn’t especially deep in the Republican state. West Virginia candidates have to file their announcement by Jan. 27, 2024.

Michigan Sen. Gary Peters, who chairs the Senate Democratic campaign arm, said in a recent interview with CBS News that he was urging Manchin to run again, because “if Joe Manchin runs, he will win.”

In a written statement, President Joe Biden praised Manchin as a tireless advocate for West Virginia and instrumental lawmaker who supported major gun control, infrastructure and energy laws and voted to confirm Supreme Court Justice Ketanji Brown Jackson.

“For more than forty years – as a state legislator, a Secretary of State, a Governor, and a Senator – Joe Manchin has dedicated himself to serving the people of his beloved West Virginia,” Biden said. “During my time as Vice President and now as President, Joe and I have worked together to get things done for hardworking families.”

GOP favored in election map

The Senate reelection map is much more favorable for Republicans, who are defending safe seats, than for Democrats, who are trying to hold on to 23 seats, several of which are in purple states.

The Cook Political Report with Amy Walter had placed Arizona, Ohio and West Virginia Senate seats in its “toss up” category. But it moved West Virginia to “Solid Republican” following Manchin’s announcement.

Another five Senate seats are rated as “lean Democratic,” indicating those Democratic candidates are a bit safer, but will still have an uphill battle.

David Bergstein, the Democratic Senatorial Campaign Committee communications director, said in a statement to States Newsroom that the DSCC is making investments in two other Senate races in red states, Florida and Texas.

“In addition to defending our battle-tested incumbents, we’ve already expanded the battleground map to Texas and Florida, where formidable Democratic candidates are out-raising unpopular Republican incumbents and the DSCC is making investments to lay the groundwork for our campaigns’ victories,” Bergstein said.

Sens. Rick Scott of Florida and Ted Cruz of Texas are up for reelection. In 2018, Cruz won with 50.9% of the vote over his Democratic challenger and Scott won his first Senate election over longtime Democratic incumbent Bill Nelson with 50.1% of the vote.

Manchin barely won his reelection bid in 2018, when he garnered 49.6% of the vote, beating out his Republican opponent by slightly more than 19,000 votes. That was a significant drop from 2012, when Manchin won election with 60% of the vote.

West Virginia’s Republican Sen. Shelley Moore Capito, on the other hand, won reelection in 2020 with 70% of the vote and former President Donald Trump won the state in 2016 and 2020 with wide margins.

Senators and states

In the two states still regarded by Cook as toss-ups, Arizona and Ohio:

• Arizona Sen. Kyrsten Sinema, who last year switched from being a Democrat to registering as an independent, faces long odds of winning reelection, though that race will include a registered Democrat. Sinema has not yet said if she will run again.

• Ohio Democratic Sen. Sherrod Brown, who is seeking reelection, won in 2018 with 53.4% of the vote over his Republican opponent, though the state has turned redder in the six years since that election. Ohio Republican Sen. J.D. Vance won election during 2022 with 53% of the vote and Trump won the state in 2016 and 2020.

Democratic candidates running in Michigan, Montana, Nevada, Pennsylvania and Wisconsin — all of which are rated as “lean Democratic” by The Cook Political Report — are rated as likely to do slightly better than their colleagues in the “toss up” category, though not by much.

The Michigan seat will be open next year following Sen. Debbie Stabenow’s decision to retire, but the other four are held by Democrats seeking reelection:

• Montana Democratic Sen. Jon Tester narrowly won reelection in 2018 with 50.3% of the vote, though Trump won the state in 2016 and 2020. And Daines won his reelection to the U.S. Senate in 2020 with 55% of the vote.

• Nevada Democratic Sen. Jacky Rosen won election in 2018 with 50.4% of the vote. The Democratic presidential candidate won that state in 2016 and 2020.

• Pennsylvania Democratic Sen. Bob Casey Jr. won reelection in 2018 with 55.7% of the vote. The commonwealth voted for Trump in 2016, but for Biden in 2020.

• Wisconsin Democratic Sen. Tammy Baldwin won reelection with 55.4% of the vote in 2018. Her Republican colleague, Republican Sen. Ron Johnson, won his last reelection in 2022 with 50.4% of the vote. The Badger state voted for Trump in 2016 and Biden in 2020.

Republicans are running for re-election in 11 Senate seats they currently hold, though all of those races are rated as either “likely Republican” or “solid Republican” by The Cook Political Report.

Energy Committee shuffle

A major part of Manchin’s legacy will be his role in developing energy policy. As the chair of the Senate Energy and Natural Resources Committee, he wielded an even more outsized role on those issues than as an influential swing vote on most legislation.

But holding major financial interests in the coal industry of his conservative home state, his views on energy and environmental issues were often out of step with his Democratic colleagues.

The next Democratic leader of that committee would almost certainly be more in line with most Democratic voters’ views. New Mexico’s Martin Heinrich, who, in a rare move in the congenial Senate, publicly questioned Manchin’s fitness for the position in July 2022, would likely be a frontrunner for the chair.

The top three Democrats on the panel by seniority all chair other top committees and may be uninterested in the post.

Oregon’s Ron Wyden chairs the tax-writing Finance Committee, a more powerful and desired role in Washington than Energy Committee chair.

Washington’s Maria Cantwell previously chaired the Energy Committee, but in 2021 dropped her spot as the top Democrat on that panel to take the top position on the Commerce, Science and Transportation Committee.

Vermont’s Bernie Sanders leads the Health, Education, Labor and Pensions Committee, which Sanders may view as more in line with his policy priorities.

Heinrich, fourth in seniority on the Democratic side, chairs the Joint Economic Committee, a shared committee with the House considered more minor than the Senate’s standing committees.

Heinrich has built a reputation on energy and climate issues, and was a finalist as Biden’s choice to lead the Interior Department.

Heinrich worked at a nuclear reactor in college at the University of Missouri-Columbia, and started his career in a research lab on directed energy after graduating with a mechanical engineering degree.

Like virtually all other members of the Senate Democratic caucus, Heinrich is considered more progressive on energy and climate issues than Manchin.

In the summer of 2022, when it appeared Manchin’s opposition would doom Biden’s proposal for a massive renewable energy spending package, Heinrich blasted the chairman in a post to the site then known as Twitter.

Less than two weeks later, Manchin authored, with Majority Leader Chuck Schumer, a major energy, taxes and health policy bill that included historic tax breaks for renewable energy. The measure, which was called the Inflation Reduction Act and also included some provisions to protect fossil fuel development, passed along party lines.

In a written statement to States Newsroom on Thursday, Heinrich praised Manchin’s work on that law, which he called the West Virginian’s “signature accomplishment,” as well as major conservation measures and the bipartisan infrastructure law in 2021.

“His?leadership was instrumental in finalizing each of these laws,” Heinrich said. “The Inflation Reduction Act in particular—Chairman Manchin’s signature accomplishment—is by far the biggest American?manufacturing accomplishment in decades.”