Energy looms large in West Virginia — the second-largest coal producer in the U.S., after Wyoming, and a state that has faced "deep, deep challenges" in recent decades, said Barry Rabe, a nonresident senior fellow at the Brookings Institution think tank in Washington. The coal industry has suffered in large part by the advent of hydraulic fracturing, or fracking, which pushed down the price of energy across the board.
"A big part of what they maintain in their economy has been energy production, and that's been coal, oil and natural gas," Rabe said. "It's pretty hard if you're going to be representing a state like West Virginia that you get way out ahead ... on anything that would challenge the dominance of fossil fuels."
Manchin's position as the pivot point for many votes — particularly on energy and the environment — gives him "unusual clout," Rabe said.
"If you look at his record over the last decade, Manchin is someone who may well be likely to break from majority Democratic voting sentiments," he said. "He's got a voting record overall that looks more Republican than any other Democratic senator."
Now that Congress has passed Biden's $1.9 trillion COVID-19 relief package, lawmakers in the coming months will turn to the president's infrastructure, climate and energy agenda.
Biden campaigned on a $2 trillion Build Back Better plan that would put the U.S. on an "irreversible path" to achieve a carbon pollution-free power sector by 2035 and net-zero emissions by 2050. It also includes efforts to modernize infrastructure, such as building at least 500,000 EV charging stations nationwide.
The White House said details of the agenda are being finalized.
Manchin, who is chairman of the Senate Committee on Energy and Natural Resources, has said he won't support passing the president's next big package through reconciliation, or a simple majority.
"He wants to get 60 votes. He wants to get 10 Republicans to come across," said Christian Renaud, research director at S&P Global's 451 Research. "He's ready to make concessions on this gigantic, multitrillion-dollar infrastructure and energy bill."
But Manchin is just "one of the linchpins to getting any legislation passed," and several moderate Democratic senators such as Kyrsten Sinema of Arizona also will be key votes, said Kristin Dziczek, vice president of industry, labor and economics at the Center for Automotive Research in Ann Arbor, Mich.
"His power has increased, but so has every other centrist," she said.