Washington Governor Jay Inslee, who made fighting climate change the central theme of his presidential campaign, announced Wednesday night that he is ending his bid for the 2020 Democratic nomination. Inslee announced his decision on MSNBC's "The Rachel Maddow Show," admitting it's become clear that he won't win.

Inslee has kept open the option of running for a third gubernatorial term throughout his presidential campaign, but didn't immediately say what his political plans were.

"This is sort of the bookends of my campaign," Inslee said on MSNBC. "We started seeing that climate change had to be the number one job of the United States. I felt very good saying that the first days of my campaign. I feel very good saying that now. And the reason is this is has just become more urgent — a billion tons of ice melted in Greenland the other day. But we also have had so many people that I have met who are inspiring, who want us to act, who have helped me. We have had 130,000 people help me in this campaign."

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"But it has become clear that I am not going to be carrying the ball, I am not going to be the president, so I'm withdrawing tonight from the race," he added.

Gov. Jay Inslee speaks during the first Democratic primary debate Miami, Florida, on June 26, 2019. Getty

Inslee, 68, is the latest Democrat to end his presidential bid, following U.S. Rep. Eric Swalwell of California, who withdrew from the race last month. And former Colorado Governor John Hickenlooper dropped his bid just last week.

In an email to supporters, Inslee said he would have more to say about his next steps "in the days ahead." Some signs point to a third run for governor. That election will also be held in November 2020.

"I can assure you that I will continue to lead, to demand bold action, and to do everything in my power to ensure the fight to defeat climate change stays at the top of the national agenda." Inslee wrote. At the inception of his campaign, Inslee had promised to keep climate change in the national conversation, saying that in previous election cycles the issue had received "little attention" from the candidates, the Democratic Party or the media.

"Many of the campaigns started with little attention to climate, but since our campaign began, we've seen almost every serious candidate put out a climate plan," his email said. "Most importantly, we have introduced a detailed and comprehensive policy blueprint for bold climate action and transformation to a clean energy economy."

Inslee also unsuccessfully fought with the Democratic National Committee early in the summer over holding a debate specifically focused on climate change.

Several fellow Democratic candidates weighed in on the governor's decision to withdraw. Senator Bernie Sanders wrote in a tweet, "Congratulations to @JayInslee on his impactful campaign to bring the climate crisis to the forefront of the national conversation."

While Inslee had qualified for the first two presidential debates this summer, he struggled to gain traction in the crowded Democratic field and was falling short of the requirements needed to appear on two high-profile stages next month: the third DNC debate in Houston and a CNN town hall focused on climate change, Inslee's key issue.

He had recently hit one of the markers — 130,000 unique donors. But he had yet to reach 2% in any poll and would have needed to hit that level of support in four qualifying polls.

Inslee is a former congressman and served as Democratic Governors Association chairman in 2018, when the party flipped seven Republican-held gubernatorial seats. He kicked off his campaign in March in Seattle, standing in front of a blue-and-green campaign logo with an arc of the Earth, declaring climate change the nation's most pressing issue.

Inslee was a champion for the clean energy industry in Congress and wrote a book on the topic. And he's pushed for state policies to curb greenhouse gas emissions blamed for global warming. On the day he announced his presidential bid, the state Senate passed a key piece of his legislative climate agenda, a measure that seeks to eliminate fossil fuels like natural gas and coal from the state's electricity supply by 2045.

The measure, later passed by the House and signed by Inslee in May, made Washington the fourth in the nation to establish a mandate to provide carbon-free electricity by a targeted date. A few additional states have enacted legislation related to clean energy requirements since May, according to the National Conference of State Legislatures.

In addition to pushing for a dedicated debate on climate change, Inslee's campaign has been rolling out climate proposals, including calling for the nation's entire electrical grid and all new vehicles and buildings to be carbon pollution free by 2030. He's also proposed a clean break between the federal government and the fossil fuel industry, ending tax breaks for oil companies and banning all drilling and extraction on federal lands and beneath federal waters.

Inslee released his sixth and final climate proposal, a plan focused on agriculture and farmers, hours before he announced he was dropping out of the race.

In a video released Tuesday on Twitter, Inslee thanked supporters for helping him pass the 130,000 individual donor mark.

"Together we have put the climate crisis front and center in the 2020 race," he said. "And thanks to you, every candidate knows they have to have a robust plan to defeat the climate crisis."

Governors in Washington state aren't subject to term limits, though most haven't served more than two terms. The last three-term governor in Washington was Republican Governor Dan Evans, who served from 1965 until 1977.

While the filing deadline for the state's 2020 elections isn't until next May, three Democrats have already signaled they will run for governor if Inslee doesn't: Attorney General Bob Ferguson, Commissioner of Public Lands Hilary Franz and King County Executive Dow Constantine. The political dominos continue with Democratic candidates lining up to run for attorney general and lands commissioner if Ferguson and Franz end up not seeking reelection to their posts.

A few Republicans have already announced plans to run for governor, including Phil Fortunato, a state senator, and Loren Culp, the police chief of Republic, in eastern Washington. A Republican has not occupied the governor's office in more than three decades.

Tim Perry contributed to this report.