This from Grist:
How Green Is Your Candidate?
Where the presidential candidates stand on climate and energy issues
All of the Democratic presidential candidates put energy independence and climate change among their top-tier issues. They all support carbon cap-and-trade systems of varying strengths. They all at least gesture at renewable energy and hybrid cars. Most support ethanol and "clean coal." The aggressiveness of their climate and energy plans rises inversely with their chances of winning -- the better the chances, the weaker the plan.
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If I were a one-issue voter, Richardson would most likely grab my vote, here. Of course, I'm not -- so I'd want to know lots more about his stands on other things before making up my mind. Given the splash he hasn't made among the rest of the population, it's probably a moot point, anyway.