WASHINGTON (AP) - For Republican presidential contenders who once supported combatting global warming, the race is heating up.

Most of the GOP White House hopefuls have stepped back from their previous positions on global warming. They're catering to an activist right wing that questions the science of climate change and disdains big government.

When they were governors, Tim Pawlenty, Jon Huntsman and Mitt Romney all supported regional plans to curb greenhouse gases.

Romney changed his position in 2005. Pawlenty has apologized for it.

Huntsman has said the time isn't right because of the economy. Newt Gingrich once called for action on climate change. Now, conservatives are demanding an apology from him.

On Thursday, New Jersey Gov. Chris Christie said he's pulling his state out of a regional plan to reduce greenhouse gases.

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