The Sierra Club came under attack from other environmental activists for accepting money from Mr. McClendon, whose company has a financial interest in killing off its competition but burns a fossil fuel itself. Mr. Nilles, the director of Beyond Coal, now views it as a mistake. “We would not do it again,” he said.

Other deep-pocketed donors have stepped in, including Mr. Bloomberg, whose intervention has infuriated Kentucky officials like Mr. Adkins, the legislator.

“Mayor Bloomberg should stay in that high-rise condo or his mansions,” Mr. Adkins said, “and eat his caviar while we keep his lights on in New York City.”

Big Coal has hardly conceded defeat in this multifront war.

The industry has increased political campaign contributions in the last four years to historic levels, with 80 percent of those donations going to Republicans, according to the Center for Responsive Politics. Companies like Arch Coal, which used to spend only about $100,000 a year on lobbyists in Washington, invested $5.7 million to push its case during the first three years of the Obama administration.

And even as American Electric Power plans to close 5 of its 21 coal-burning plants and rely much more on natural gas, it still intends to retrofit 12 plants. That means it will be burning coal for years to come. A rise in natural gas prices could also slow the decline of coal as a power source. So the company has joined with old allies in Washington to try to delay the new rules and block any future ones.

The industry and its supporters have also gone to court, filing lawsuits challenging E.P.A. rules that limit pollution from coal-burning plants from crossing state lines and the mountaintop mining rules that are holding up new permits in Kentucky and West Virginia — legal fights that the industry has had some success with so far.

But the regional agency that coordinates electric power delivery in the mid-Atlantic and the Midwest cannot wait for the battles to be resolved. This month, it auctioned off the rights for utility companies to supply electricity that will be needed to make up for what is lost through coal plant retirements. Most of the new power is fueled by natural gas.

“It’s an unprecedented transition,” said Michael J. Kormos, senior vice president for operations at PJM Interconnection, the regional group that coordinates power delivery for 60 million people in 13 states. “But whatever happens, we have to make sure we keep the lights on.”