5. Mark Kirk
U.S. senator from Illinois
Before: In June 2009, while a member of the U.S. House, he was one of just eight Republicans to vote in favor of the Waxman-Markey climate and clean energy bill. “There is now a growing scientific consensus that the level of atmospheric carbon dioxide affects average temperatures,” he wrote in a letter to a constituent at the time.
After: Just three months later, while running for a Senate seat, he said he would oppose the same bill if it came up for a vote in the Senate. As he explained in January 2011, “The consensus behind the climate-change bill collapsed and then further deteriorated with the personal and political collapse of Vice President [Al] Gore.”