Politico’s Darren Samuelsohn reports that some greens are donating to Mitt Romney in the hopes he’ll go back to caring about climate change if elected. And Romney does have one big idea for cutting carbon emissions. But political science research suggests he’s not likely to take it up.

Probably not a closet green (Gerald Herbert/AP)

It’s also an idea that’s gaining favor among greens and think tanks as a deficit-reducing measure. As Rep. Henry Waxman explained in a recent interview with Ezra Klein, a price on carbon is one way to bring down the debt without slashing Medicare or defense spending too heavily. Last year, four of the six groups that sketched out deficit plans for the Peter G. Peterson Solutions Initiative ended up advocating a carbon tax — including, note, the conservative American Enterprise Institute.

That said, for Romney to swivel around and support a carbon tax if he came into the the White House would be somewhat unprecedented. As political scientist Jonathan Bernstein has argued at length, presidents usually stick closely to the policies and positions they espoused on the campaign trail. And Romney on the stump hasn’t sounded like the sort of politician ready to support a tax on fossil fuels — or fret much about global warming at all. Here he was just this past October: “My view is that we don’t know what’s causing climate change on this planet and the idea of spending trillions and trillions of dollars to try and reduce CO2 emissions is not the right course for us.”

About the only thing Romney does explicitly endorse on the climate front, judging from his campaign site, is “national investment in basic research and advanced technology.” He’s spoken favorably, for instance, about ARPA-E, the Energy Department program that funds long-shot energy concepts like futuristic battery materials and plants bio-engineered to replace oil. So if Romney’s environmental donors are hoping for a Republican who might boost R&D, that’s a reasonable bet. Anything else is quite speculative — and, based on history, quite unlikely.