Tim Pawlenty.Photo: Gage Skidmore2.  Tim Pawlenty

Presidential candidate, former governor of Minnesota

Before: “I support a reasonable cap-and-trade system,” he said in February 2008.

After: “As to climate change, or more specifically cap-and-trade, I’ve just come out and admitted it — look, it was a mistake, it was stupid,” he said in March 2011.

Read more about Pawlenty and climate.