Jane Mayer, writing for the New Yorker:
Starting in 2008, a year after the Supreme Court ruled that the Environmental Protection Agency could regulate greenhouse gasses as a form of pollution, accelerating possible Congressional action on climate change, the Koch-funded nonprofit group, Americans for Prosperity, devised the “No Climate Tax” pledge. It has been, according to the study, a component of a remarkably successful campaign to prevent lawmakers from addressing climate change. Two successive efforts to control greenhouse-gas emissions by implementing cap-and-trade energy bills died in the Senate, the latter of which was specifically targeted by A.F.P.’s pledge. By now, four hundred and eleven current office holders nationwide have signed the pledge. Signatories include the entire Republican leadership in the House of Representatives, a third of the members of the House of Representatives as a whole, and a quarter of U.S. senators.
Oh, that’s why.