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Although their states could benefit from an increase in the use of natural gas as coal is phased out under the new emissions standards, they will have to fend off criticism from Republican rivals that the Obama administration’s EPA is hostile to energy and business interests.

The coal debate also will reverberate across the campaign trail for Rep. Nick J. Rahall II, West Virginia Democrat, who has had to deal with the fallout from Mr. Obama’s energy policies as he tackles one of the toughest races of his nearly 40-year career.

The EPA rules also threaten to step on Democrats’ national campaign message that focuses on jobs and the economy.

Providing fodder for the EPA’s critics, a U.S. Chamber of Commerce study released last week calculated that the emissions reduction goals set by the Obama administration would reduce the nation’s gross domestic product by $51 billion a year, cost 224,000 jobs and increase American electricity bills by $289 billion from 2015 to 2030. EPA officials have disputed the Chamber of Commerce estimates, and other critics note that the projected costs amount to only 0.003 percent of a $17 trillion economy.

The coal industry lobby also warns that an increased reliance on natural gas will result in unreliable electric supplies and mass blackouts.

“This administration has largely turned a deaf ear to those states that are most affected,” said Laura Sheehan, senior vice president of communications at the American Coalition for Clean Coal Electricity, an industry lobbying firm. “Their goal is to bring about the end of coal-based electricity in the United States.”

In response to questions about the administration’s climate change agenda, Democratic Congressional Campaign Committee spokesman Josh Schwerin stuck to the party’s message.

“While every candidate runs with their own message in their own district, Democrats across the country are focused on strengthening the economy by creating good jobs, supporting equal pay for women, investing in infrastructure and putting the middle class ahead of special interests,” he said.

“As Democrats zero in on strengthening the economy for middle-class families, Republicans have abandoned any pretext whatsoever of caring about jobs or the economy and now have a singular focus on conspiracy theories and partisan political games. It’s abundantly clear to voters which party is focused on the economy and which one is focused on political gamesmanship,” Mr. Schwerin said.

Mr. Obama also has sided with environmentalists to the detriment of red state Democrats by repeatedly delaying a decision on whether to build the Keystone XL oil pipeline from Canada to the Gulf Coast in Texas.