The coal industry has always been a strong 'red' supporter . . . . . . Unions conversely, are frequently not.
So who does the United Steelworkers Union and United Mineworkers of America support?
Both these eminate from strongly republican industries but have a vested interest in the democratic party. Initially, both endorsed John Edwards but since his departure from the presidential race neither union has yet to support a second candidate. Both of these are large unions with significant representation in states like Ohio, Illinois, Pennsylvania, and Michingan etc.
I expect both to follow their Union ties over industry and support the democratic presidential candidate . . . . but unlike other Unions, not until a candidate has finally been identified.