Polls consistently show that young people are the strongest supporters of measures to combat climate change. They are also the least likely to vote, especially during off-year elections.

The Environmental Defense Fund plans to test whether it is possible to change that, starting with a new $2 million initiative in Colorado, where one of the closest Senate contests in the nation is being fought this year.

Among those coordinating the new EDF effort will be Mitch Stewart, who was battleground states director for President Obama's 2012 re-election campaign.  He argues that many of the same tactics that brought young people to the polls for a candidate they care about can be employed for an issue as well.

Colorado's a state where young voters are particularly prone to stay home when there is no presidential contest on the ballot. Between 2008 and 2010, for instance, youth turnout rates dropped by more than half, from 51 percent to only 24 percent.

That dropoff made Colorado a particular focus for Obama's 2012 re-election campaign, Stewart said. That year, they succeeded in bringing the number almost to 2008 levels, and Obama won Colorado by almost 5 percentage points.

Through an aggressive digital and social media effort, the campaign that EDF is calling Defend our Future will look to convince at least 100,000 millennials in Colorado to sign a pledge to vote and to press candidates on climate change, and then to share it on their social networks. The Web campaign will be augmented by an on-the-ground operation at the state's two largest campuses, the University of Colorado Boulder and Colorado State University.

The organization will then track those who pledged to see whether they actually turn up at the polls in November. If the Colorado campaign works, EDF officials said they plan to repeat it across a broader map in future elections.

"Ultimately, the political system is going to have to recognize the reality of the public interest," said Jeremy Symons, EDF's senior director for climate policy.

EDF said the campaign is nonpartisan, but Colorado is a place where the two parties' differences on the climate issue are defined in high relief.

Embattled Democratic incumbent Sen. Mark Udall argues that climate change is threatening Colorado's way of life, and requires urgent action. His opponent, Republican congressman Cory Gardner, has said he believes that climates shifts are occurring, but that the role of humans in causing that has been overblown by the media.