For years, environmentalists have been trying to make climate-change denial a vulnerability for Republicans.
In 2013 Organizing for Action, the advocacy arm pushing the Obama administration's agenda, targeted climate deniers in Congress. And the League of Conservation Voters spent millions of dollars on an ad campaign to "hold climate-change deniers accountable."
Now, there's some evidence it's paying off — specifically, that along with other defining issues like gun-control, gay marriage, and immigration, the media is increasingly asking GOP candidates about their views on climate change.
At a Thursday night debate in South Dakota, for instance, Republicans running for the Senate were asked to weigh in on climate change. Earlier this week, Sen. Marco Rubio of Florida caused a tremendous stir when he announced he doesn't believe human activity makes a major contribution to the earth's warming climate. (Rubio later told The Miami Herald's Marc Caputo, "I think all science deserves skepticism.")
Before that, Democratic Rep. Gary Peters, who is running for the Senate in Michigan, called on his Republican rival Terri Lynn Land to state for the record whether she believes the science behind man-made climate change. He even announced to The Washington Post's Greg Sargent that he intends to make climate change a key issue in the race.