Washington Gov. Jay Inslee announced Wednesday he is exiting the race for the Democratic presidential nomination. Inslee has made addressing climate change the focal point of his campaign for the Oval Office, dubbing himself as the “climate candidate” when he toured a Cedar Rapids solar energy company in March. Wednesday morning, he released his sixth part of a 10-year proposal to slash emissions and invest in renewable energy. In his stump speeches and interviews, Inslee has said all other political issues depend on successfully fighting climate change.

Inslee first announced his departure from the presidential primary in an interview with MSNBC’s Rachel Maddow. In an email to supporters an hour later, the Inslee campaign cited lackluster polling as the reason for not continuing the race. Inslee hit the required number of unique donors to qualify for the September debates, but hadn’t yet reached the polling threshold to fulfill the second requirement to get on the debate stage.

“…it became clear that we would not meet the DNC’s polling threshold, thus we would not have been invited to the fall debates,” the email read. “As a result, I don’t believe we can compete for the attention and exposure needed to have a reasonable shot at the nomination.”

In Iowa, about 1 percent of respondents picked Inslee for their top choice according to a June Iowa Poll, conducted by the Des Moines Register and Mediacom.

In Iowa City, Inslee outlined his higher-education plans to University of Iowa faculty during a July meeting at Hamburg Inn No. 2.

The governor’s announcement comes a week after former Colorado Gov. John Hickenlooper announced he would be dropping his nomination bid. Twenty-two candidate remain in the race.

Inslee also called on the Democratic National Committee to put on a debate solely about climate change. Though the DNC refuted his efforts, media outlets have scheduled town halls with multiple candidates on the subject.

“I know you agree that our mission to defeat climate change must continue to be central to our national discussion — and must be the top priority for our next president,” the email read. “But I’ve concluded that my role in that effort will not be as a candidate to be the next president of the United States.”