Positive polling conducted by a Democratic group and later published by The Denver Post suggested Hickenlooper would be the favorite if he jumped into the Senate chase. More than ten Democrats are already in the primary.

The 314 Action Fund even launched a “Draft Hickenlooper” campaign. Executive Director Josh Morrow applauded what he sees as Hickenlooper’s track record of reaching across the aisle.

“The only way to send Mitch McConnell to the minority is with a win in Colorado, and John has the best opportunity to defeat America’s most vulnerable senator,” Morrow said in a statement.

Hickenlooper persisted in his White House quest as long as he could. He had originally vowed to say in the race through the Iowa caucuses in early February, but as of July, his campaign had less than a $1 million on hand and there was staff shake-up.

With some exceptions, money left over from the presidential campaign can be transferred to a senate campaign, if he decides to get in. The money could also be donated to charity or transferred to another candidate, provided it doesn't exceed normal contribution limits. What you can't do is use excess campaign funds for personal reasons.

Hickenlooper did make some headlines on the campaign trail, like when he got booed at California’s Democratic Convention when he took the stage and said socialism wasn’t the answer.

In the Detroit Democratic Presidential Primary Debate, Hickenlooper said policies like Medicare For All or the Green New Deal approach to climate change "are disasters... you might as well FedEx the election to Donald Trump." That prompted a response from Sen. Bernie Sanders, who raised his arms in frustration.

"Throw your hands up," Hickenlooper said, raising his.

"All right," replied Sanders, doing just that.

"Oh ho, I can do it," came the Hickenlooper response as the crowd in the Fox Theater roared.

Now all eyes will turn to the remaining field of 23, which includes billionaire Tom Steyer who jumped into the race the day after Swalwell got out. The loud suggestions that Hickenlooper switch campaigns may have also deflected critical attention from fellow-Coloradan and presidential candidate Sen. Michael Bennet — but it could also help.

“The lane that Hickenlooper and Bennett were traveling down was the pragmatic progressive lane and Joe Biden is sort of firmly entrenched there, but if he stumbles, there is an opportunity for someone else to emerge, and Bennet certainly would have that opportunity,” said Democratic political strategist Curtis Hubbard, who has launched a draft Hickenlooper campaign for the U.S. Senate race. “It is a long shot, but one fewer candidate in that lane certainly helps [Bennet’s] chances.”

The next real test will be the cutoff for the September Democratic presidential debate. So far, only nine candidates have made the grade. Bennet isn’t among them.

"John was a great mayor and governor, and helped shape the presidential race with his pragmatic viewpoint," Sen. Bennet said in a statement in response to Hickenlooper's exit. "He provided a valuable voice in this primary, bringing the ideas and solutions he successfully championed in Colorado to the national debate."