Coal is a major pollutant; many parents worry about mercury in vaccines, but the fact is that all of us breath in much more mercury due to pollution from coal plants. And of course this mercury is present in the earth and water too, and throughout the food chain. This has a much bigger impact, at least in the short term, than carbon dioxide.
That said, 50% of our energy is generated from coal, so there’s no way to just get rid of it now. I agree that solar & wind energy are great “green” sources, but right now only about 1% of our electricity energy comes from wind & much less than that comes directly from the sun. Wind & solar cannot be generated everywhere, and neither is available all the time, so they cannot provide most of our electricity.
Personally I think the answer in the medium term is more nuclear power plants. Currently 20% of our energy comes from nuclear, which produces no pollutants (except waste heat) and no greenhouse gases. Both candidates want to build more nuclear plants; Obama just wants to resolve waste disposal issues first, especially the status of the Yucca Mountain disposal site.