If Sean Casten had talked about climate change once during his campaign, that would have been more than most Democrats running for Congress. But Casten didn’t talk about climate change just once, or even merely ten or twenty times, as he sought to flip Illinois 6th Congressional District from red to blue. He made it the center of his entire campaign.

“After years fighting climate change as an entrepreneur, I’m now determined to fight it as the next member of Congress,” reads Casten’s Twitter bio, updated to reflect his victory on Tuesday. A scientist, environmental writer, and the founder of a successful renewable energy business, Casten talked repeatedly about global warming on the campaign trail and regularly called out his opponent—six-term incumbent Republican Representative Peter Roskam—for being weak on the subject.

Casten’s focus on climate was mostly overlooked in the widespread coverage of his five-point upset of Roskam, who once referred to climate change as “junk science.” But it’s an important factor, considering the Democratic Party’s prevailing logic on the subject. Knowing that global warming can be a polarizing issue, most Democrats running in red or purple districts this year strategically avoided talking about it. They feared, according to The New York Times, that “highlighting climate change risks handing conservative voters a motivating issue to turn out against them.”

So why didn’t Casten heed that logic in Illinois’ 6th, given that it’s been in Republican hands for more than 40 years?



“I’ve never run for any office before,” Casten told me in a Friday phone interview. “But what I have done is spent the last 20 years doing something about climate change. So I wasn’t going to suddenly turn into a different beast on the day I ran for office.” He said he didn’t receive any warnings from Democratic Party officials about his campaign platform. “I think its a misconception that the party controls messaging,” he said.