Ads displayed at Washington subway stops and airing on national television call "clean coal" a myth. Tell that to President Obama, his Cabinet secretaries and members of Congress. Five months into an advertising war on coal, the phrase "clean coal" not only endures, it has become political shorthand. Everyone -- from Democratic Sen. Kent Conrad of North Dakota to Interior Secretary Ken Salazar -- refers to clean coal or clean coal technology. The word war over coal is escalating. There are billions of dollars at stake, as Congress moves toward historic legislation that could decide winners and losers in the green energy economy.