During his first 18 months as governor of Massachusetts, Mitt Romney spent considerable time hammering out a sweeping climate change plan to reduce the state's greenhouse gas emissions.

As staff briefed him on possible measures and environmentalists pressed him to act, Romney frequently repeated a central thought, people at those meetings said: That climate change is occurring, that the United States has the resources to handle its vast impact but that low-lying poor countries like Bangladesh would suffer greatly.

"It was like a mantra with him," said a person who attended those meetings who declined to be identified because of the sensitivity of the topic. "His Cabinet members would look at him like, 'What?' He was the radical in the room."