John Hickenlooper is launching a bid Thursday to unseat Republican U.S. Sen. Cory Gardner, exactly one week after pulling out of his run for the presidency.

“I’ve always said Washington was a lousy place for a guy like me who wants to get things done – but this is no time to walk away from the table,” the former governor of Colorado says in his announcement video, posted at hickenlooper.com. “… I’m not done fighting for the people of Colorado.”

In the video, filmed at the Denver brewpub he founded, Hickenlooper echoes his presidential pitch to voters, which focused on ending the conflict in Washington. And he promises to work on fighting climate change, prescription drug prices and economic inequity.

“We ought to be working together to move this country forward and stop the political nonsense,” he says.

His entry is certain to upend the nascent Democratic Senate primary, which already includes 11 candidates. Early polls have shown Hickenlooper outpacing Gardner in a hypothetical matchup. However, he is not expected to clear the Democratic field. Several Senate candidates pledged to stay in last week after Hickenlooper dropped out of the presidential race.

Partisan control of the U.S. Senate hangs on a handful of key races, including Colorado’s. Gardner is considered one of the most vulnerable Senate Republicans up for re-election in 2020, and national Democrats, who want to leave nothing to chance, leaned heavily on Hickenlooper to run against him.

By entering the Senate primary, Hickenlooper fulfills their wishes. However, his candidacy could dash the dreams of Colorado progressives who had hoped the seat would be filled by a woman or person of color — adding diversity to Colorado’s Washington delegation.

Hickenlooper’s decision also reverses months of public statements bluntly rejecting the idea of a Senate run. In February, he said, “I’m not cut out to be a senator.” In May, he said he would “be a difficult candidate” for Senate.

Republicans have been preemptively criticizing Hickenlooper since he abandoned his White House bid.

“John Hickenlooper is desperate to redeem himself after flopping on the national stage, but we think he said it best just a few months ago: he is ‘not cut out’ for the Senate,” National Republican Senatorial Committee spokesperson Joanna Rodriguez said Wednesday. “This crowded Senate field has been in a race to the left, and Hickenlooper’s quixotic presidential bid did not do him any favors in proving he can compete in any race in 2020.”

Curtis Hubbard, a Democratic strategist who publicly lobbied Hickenlooper to enter the race, said the candidate will be able to walk back those comments with ease.

“When you’re running for one office, it’s tough to answer that you would be interested in another office. And in this instance, it’s clear from the public outpouring for him to enter the race and from his accomplishments in Colorado that the Senate campaign is the right place for John Hickenlooper,” Hubbard said. “He’s always been one to look at the facts and then make a decision. Having looked at the facts, it would not surprise me that he understands the right decision is to enter the race and make Cory Gardner a one-term senator.”

The former governor’s entry makes an even dozen candidates in the Democratic race for the Senate. He is sure to reorder the top tier, which has been led by former Colorado House Speaker Andrew Romanoff and former state Sen. Mike Johnston in early polling. Johnston has also led the race in fundraising, bringing in more last quarter than Hickenlooper’s presidential campaign.

Candidates in the race’s lower tier, made up primarily of progressives, are sure to criticize Hickenlooper’s moderate stances. Many have expressed frustration at efforts to recruit the centrist white male rather than support a progressive woman. Colorado has never elected a woman to the Senate.

Meanwhile, Gardner’s campaign on Wednesday aimed to lump Hickenlooper with the rest of the Democratic field.

“To us Governor Hickenlooper is just another liberal in the clown car,” Casey Contres, Gardner’s campaign manager, said in a statement. “Whoever their party nominates will be wildly out of step with Colorado and we look forward to facing them in the general election.”