In the week since Texas Gov. Rick Perry launched his bid for the White House, he has exploded onto the national scene, firing off provocative comments, touting his "Texas miracle" and drawing shots from his fellow GOP candidates.
The latest episode of candidate-on-candidate banter came this week after the increasingly-vocal Jon Huntsman shot back at Perry for comments the he made Wednesday that discounted global warming as a "scientific theory that has not been proven."
Huntsman, who has supported emissions regulations to stave off global warming, took a jab at Perry via twitter, saying, "To be clear. I believe in evolution and trust scientists on global warming. Call me crazy."
Despite their shared party affiliation, Huntsman and Perry stand on starkly different sides of the climate debate.
As the governor of Utah, Huntsman pushed for cap-and-trade policies to limit carbon emissions, even appearing in a 2007 Environmental Defense Action Fund television ad urging Congress to cut greenhouse gas emissions.
Perry, on the other hand, sued the Environmental Protection Agency for trying to regulate carbon emissions, regulations he said would amount to "sweeping mandates and draconian punishments, undoing decades of progress, painting entrepreneurs as selfish and destroying hundreds of thousands of jobs in the process."
"What distinguishes Rick Perry from Jon Huntsman is not whether humans are causing some global warming, but whether humans are causing significant global warming to where it is going to be a threat," said James Taylor, senior fellow for environment policy at the Heartland Institute, a free-market think tank.
Despite his steadfast support for combating climate change as a governor, as a presidential candidate Huntsman has backed away from supporting cap-and-trade, a policy that fellow candidates Ron Paul and Michele Bachmann both voted against while in the U.S. House.
"It hasn't worked," Huntsman said in a May 2011 interview with Time, "and our economy's in a different place than five years ago." Until it recovers, Huntsman said, "this isn't the moment" to push for cap-and-trade.
Policy prescriptions aside, presidential candidate Mitt Romney seems to agree with Huntsman that global warming is a man-made problem, saying at a Manchester, N.H., town hall this week that he believes "the world is getting warmer, and I believe that humans have contributed to that."
"I can't prove that, but I believe based on what I read that the world is getting warmer," Romney said, adding that "it's important for us to reduce our emissions of pollutants and greenhouse gases that may be significant contributors."
As Massachusetts governor, Romney supported a 2004 Climate Protection Plan that would reduce greenhouse gas emission by 25 percent by 2012. But in 2006, the governor pulled his state out of a similar pact that would reduce emissions by 10 percent by 2019, because he said it would cost too much.
"New England has the highest energy rates in the country, and [the plan] would cost us more," Romney told the Boston Globe after he abandoned the Regional Greenhouse Gas Initiative.
Jim DiPeso, vice president for policy and communications at Republicans for Environmental Protection, said Romney and Huntsman are taking "somewhat of a political risk" by supporting the scientific claims that global warming is a real threat.