The United Mine Workers Union has been a traditional voting base for the Democrats.
However, Obama's plan to kill the coal industry through harsh EPA restrictions on coal usage may just bring that relationship to an end; and, in doing so, ruin the lives of 20,000 active miners. But, the pain won't stop there. 40,000 retired workers and their 50,000 dependents and spouses could lose their pension benefits because there just won't be enough active workers left to support those benefits.
This is why, on October 7th, 300 miners picketed on the steps of the main headquarters of the EPA. So, I guess the President has a choice. Continue with the current course and tick off the mine workers and other sympathetic union members, or put a halt to the harsh restrictions on coal usage and tick off the environmental wing of the Democratic party. With both actions costing votes.
By the way. The pain won't only be felt by the current miners, retirees, and their families. Whole communities depend on the dollars spent by all those workers. As a result, some towns may cease to exist with people being literally forced to leave behind their homes in an attempt to survive.
Unions protest EPA power plant proposal: http://washingtonexaminer.com/unions-protest-epa-power-plant-proposal/article/2554495
Wikipedia: United Mine Workers: http://en.wikipedia.org/wiki/United_Mine_Workers