The environmental activist had urged the Democratic National Committee (DNC) to host a debate centered exclusively on climate change -- only to fail to qualify to meet polling thresholds needed to attend the party's upcoming regularly scheduled debate, as well as a CNN town hall dedicated to global warming.
Inslee revealed his decision on MSNBC, saying it's become clear that he won't win. He has kept the option of running for a third term as governor open throughout his presidential campaign but didn't immediately say what his political plans were.
Inslee, 68, became the third Democrat to end his presidential bid after U.S. Rep. Eric Swalwell of California pulled out of the primary last month followed by former Colorado Gov. John Hickenlooper last week.
The governor’s announcement came hours after he released his six policy proposal on climate change. And it also came hours after he was scheduled to speak at a presidential forum hosted by the Iowa Federation of Labor. Inslee canceled his appearance Wednesday morning, blaming flight cancellations.
On Wednesday, Fox News repeatedly attempted to contact Inslee advisers ahead of his upcoming planned visit to New Hampshire on Thursday, but the campaign went silent and didn’t return calls or emails.
"[I]t became clear that we would not meet the DNC's polling threshold, thus we would not have been invited to the fall debates," Inslee said in a press release late Wednesday. "As a result, I don't believe we can compete for the attention and exposure needed to have a reasonable shot at the nomination.
"As we turn to the future, I will have more to say about what comes next for me in the days ahead," Inslee continued. "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."
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 in New York focused on climate change.
He had recently hit one of the markers — 130,000 unique donors. But he had yet to reach 2 percent in any poll and would have needed to hit that level of support in four qualifying polls.
Other marginal candidates are in a similar position. Author and Internet favorite Marianne Williamson seemingly hasn't qualified in any polls, and Sen. Kirsten Gillibrand, D-N.Y., apparently has only qualified in one so far, with time running out.
Inslee had sought to use the debates to boost his limited profile. At the July Democratic primary debate, Inslee declared to applause, “We can no longer allow a white nationalist to be in the White House.”
Asked by Fox News after the debate if he had prepared the 'white nationalist' line in advance, Inslee explained "I thought about it driving over here this afternoon. And it’s true because the White House is such symbol of the United States, of our unity, of the fact that diversity is a strength, not a vice, the fact that we’re a nation of immigrants. But he’s really despoiled it."
Inslee also targeted the GOP, arguing "it is sad not only that he (Trump) has done that but worse that the Republican Party has enabled it. They’re complicit in his racism and his white nationalism because they will not speak against it.”
Meanwhile, prominent Democratic presidential contenders sounded notes of support for Inslee.
California Democratic Sen. Kamala Harris tweeted late Wednesday that Inslee's "voice will be missed in this primary," and that "few leaders have done more to shine a light on the climate crisis."
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 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."
Inslee didn't say whether he planned to seek a third term as governor.
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 Gov. 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.
Fox News' Paul Steinhauser and The Associated Press contributed to this report.