Hickenlooper, who struggled to break out of the narrow field of candidates, has not yet decided whether he will run for the Senate that party leaders have urged him to do, sources said. He does not plan to make an announcement on that decision Thursday.
Hickenlooper's decision was first reported by the Associated Press.
Hickenlooper focused his candidacy on inhibiting the Democratic Party's left wing. The two-year Colorado governor was a moderate voice in the main, making his opposition to democratic socialism – including Vermont Sen. Bernie Sander's political philosophy – central to his campaign.
But that strategy failed to capture momentum, and Hickenlooper's campaign lost three of its most senior staff in early July, including Brad Komar, the campaign manager. The losses signaled to many Democrats that Hickenloper's campaign was on its last legs, but the Democrats close to the governor said he wanted to stay and reconsider his chances following CNN's debate in late July.
After that debate, the former Denver mayor seemed to be struggling to make the stage in the next round of discussions in September, as he supported both the election and electoral limits for qualifying.
Hickenlooper's exit now opens the possibility that the once popular governor could run for the Colorado Senate, then challenges Cory Gardner, a Republican who is considered one of the most vulnerable legislators in 2020.
Hickenlooper spoke with Senate Minority Leader Chuck Schumer in New York about potentially challenging Gardner after the July debate. He pushed ahead with his presidential campaign after that call, and visited the Iowa State Fair in Des Moines this past weekend, along with many of the other presidential candidates.
Hickenlooper faces two questions in a Senate race, however: The governor has lamented the prospect of running for Senate and Democratic Colorado Senate candidate Mike Johnston raised more in the second quarter of 201
The former governor spent the first months of his presidential campaign to beat the idea of jumping into the Senate race.
"If the Senate is so good, how will all these senators try to get out?" Hickenlooper told CNN earlier this year, a nod to the number of Democratic senators running for president.
"The Senate does not attract me," he said. "It just doesn't attract me."
But last weekend, as his presidential campaign was nearing an end, he told CNN, "I exclude nothing."
Even in a crowded Democratic primary, Hickenlooper is still seen as the party's strongest candidate to take on Gardner. Curtis Hubbard, a Democrat strategist for a company that has worked for Hickenlooper before, recently registered domain names such as Hick4Senate.com in the hope that the former governor changed race.