Elected officials and political analysts said the president’s crackdown on coal, the leading source of industrial greenhouse gases, could have consequences for Senate seats being vacated by retiring Democrats in West Virginia and South Dakota, for shaky Democratic incumbents like Mary L. Landrieu of energy-rich Louisiana, and for the Democratic challenger of Senator Mitch McConnell of Kentucky, the Republican leader.

In ordering limits for the first time on carbon dioxide emissions from up-and-running power plants, Mr. Obama jabbed that opponents belonged to “the Flat Earth Society.” But in coal country, it was Mr. Obama who was called out of touch, with predictions of job losses and spiking energy bills.

Republicans immediately went on the attack against Democratic House members in mining states, posting Web ads with a 2008 sound bite of Mr. Obama predicting regulating carbon emissions would cause electricity prices to “necessarily skyrocket.”

Asked about the impact of the president’s actions on his own re-election prospects next year, Representative Nick J. Rahall II, Democrat of West Virginia, said, “They don’t help.”