Many of the Republican candidates vying for their party's nod to take on President Barack Obama, dismiss science in favor of strong evangelical faith, playing to a hardline conservative electorate.

Only one of the White House contenders, former Utah governor Jon Huntsman, has come out with force to proclaim a belief in man-made climate change, as he condemned his party's hostility to science.

"To be clear, I believe in evolution and trust scientists on global warming. Call me crazy," he wrote in an August post on micro-blogging site Twitter.

"The minute that the Republican Party becomes the anti-science party -- we have a huge problem," the former US ambassador to China later told ABC television's "This Week."

Other major political figures, such as New York Mayor Michael Bloomberg, have lambasted the lack of scientific faith of Republican hopefuls seeking the highest office of the world's first superpower.

"We have presidential candidates who don't believe in science. I mean, just think about it, can you imagine a company of any size in the world where the CEO said 'Oh, I don't believe in science' and that person surviving to the end of that day? Are you kidding me? It's mind-boggling!" Bloomberg told an economic forum in November.

The importance of the ultra-conservative vote, championed by a religious, anti-evolution electorate, is not lost on the contenders seeking their party's nod to face Obama in November's presidential election.

In Iowa, where caucuses kick off the months-long nominating process on Tuesday, just 21 percent of Republican voters said they believe in global warming, and 35 percent in the theory of evolution, according to a Public Policy Polling survey.

Frontrunner Mitt Romney, a Mormon former governor of Massachusetts, has reversed his pro-science support in favor of more conservative views in a bid to gain favor among the more conservative base of his party.

The shifts in position go to the core of the mistrust from his critics, who label Romney a "flip-flopper."

As Massachusetts governor, he introduced in 2004 a statewide Climate Protection Plan, billed as "an initial step in a coordinated effort to reduce emissions of greenhouse gases."

And as recently as 2007, he defended the theory of evolution.

But at a New Hampshire town hall meeting in September, he changed his tune.

"The planet is probably getting warmer. I think we're experiencing warming," Romney said. "I believe that we contribute some portion of that. I don't know how much. It could be a lot, it could be a little."

Later he sought to clarify himself, saying: "My view is that we don't know what's causing climate change on this planet."

Other candidates are not so nuanced in their views. Texas Governor Rick Perry came out strongly against climate science by claiming the data had been "manipulated" by scientists in exchange for funding money.

Representative Michele Bachmann, who in April voted for a House bill preventing further regulation of greenhouse gases, similarly spoke of "manufactured science."

Former senator Rick Santorum has also dismissed fundamental theories of man-made climate change as "patently absurd," and Representative Ron Paul has labeled the science "the greatest hoax."

The Republican Party "has a strong religious base and the evangelical vote is a significant part of that," said Andrew Kohut, director Pew Research Center for the People & the Press.

There are however, "a fair number of more secular and more moderated religious people who have doubt about global warming."

The larger issue, Kohut said, is how the federal government uses power to regulate global warming, and the issue is politicized, as Republicans fight what they see as government encroachment into the lives of Americans.