From Bloomberg:

Barack Obama will classify carbon dioxide as a dangerous pollutant that can be regulated should he win the presidential election on Nov. 4, opening the way for new rules on greenhouse gas emissions.
If elected, Obama would be the first president to group emissions blamed for global warming into a category of pollutants that includes lead and carbon monoxide.
Placing heat-trapping pollutants in the same category as ozone may lead to caps on power-plant emissions and force utilities to use the most expensive systems to curb pollution. The move may halt construction plans on as many as half of the 130 proposed new U.S. coal plants.