Mike Johnston, a former Colorado state senator and Democratic gubernatorial candidate, announced Thursday he will challenge Republican incumbent Cory Gardner for his U.S. Senate seat in 2020.
"Colorado deserves a U.S. senator who will run to our hardest problems and show the leadership to pass real progressive policy," Johnston said in a statement on his campaign website.
Johnston, 44, is the highest-profile Democrat to date to announce plans to challenge Gardner, considered among the most vulnerable GOP senators up for election next year.
Johnson said he has spent his life "running towards the hardest problems. I did it as a public school teacher and principal, as an advisor to President Obama, and then as a state senator, where I passed major legislation opening the doors of college to undocumented students, investing in renewable energy and taking on the NRA to pass common sense gun safety."
He came in third in June's gubernatorial primary, behind now-Gov. Jared Polis and former State Treasurer Cary Kennedy.
Johnston is one of several Democrats who are challenging Gardner or are considered likely candidates.
Previously announced candidates include Trish Zornio, a scientist and educator from Superior; Lorena Garcia of Denver, executive director of Colorado Statewide Parent Coalition; Navy veteran Keith Pottratz of Grand Junction; Denver activist James Blanton; and Denver pharmacist Dustin John Leitzel.
Other Democrats — including a pair of former state House speakers, Crisanta Duran and Andrew Romanoff — are expected to launch campaigns in coming months.
And John Hickenlooper has been discussed as a potential candidate if he opts against a run for president, though the former governor has maintained that he's eyeing a White House bid and isn't considering a Senate campaign.
Republicans greeted Johnston's announcement with jabs at the Democrat's performance in last year's gubernatorial primary.
"After spending $8 million to be rejected by 77 percent of Colorado Democrats less than a year ago, Mike Johnston is ready to waste more cash and lose again," said state GOP chairman Jeff Hays in a statement Thursday. "Colorado Republicans look forward to watching Johnston and his Democratic opponents clamber over each other as they race to the left over the next 17 months."
The National Republican Senatorial Committee, which Gardner chaired during the last cycle, tweeted a graphic from Johnston's gubernatorial run, tweaked to reflect his Senate candidacy.
"Another b-teamer throws their hat in the ring for what is sure to be a divisive Democrat primary," the NRSC said. "The nice thing about running until you win something is you can recycle your old campaign material."
Said Kyle Kohli, Colorado spokesman for the Republican National Committee: "It's only been a few months since Mike Johnston spent nearly $8 million to finish third place in the Democrat gubernatorial primary, and he's already running again. Johnston has proven to be far more popular with Michael Bloomberg and Silicon Valley than he is with anyone actually in Colorado."
Johnston spent $2.5 million on his primary run for governor, while Frontier Fairness, a PAC supporting his campaign, spent another $5.7 million. Bloomberg, the billionaire and former New York mayor, donated $2 million to Johnston's PAC, which also counted tech entrepreneurs among its top contributors.
Gardner, also 44, is consistently ranked as one of the most vulnerable Republican senators up for election next year, given that Colorado voted overwhelmingly for Democratic candidates in the 2018 election and favored Hillary Clinton for president in 2016 over Donald Trump by 5 percentage points.
Gardner this week endorsed President Donald Trump's re-election bid, a reversal after he opposed Trump's election in the final days of the 2016 race. While polls show Trump to be deeply unpopular among Colorado Democrats and independent voters, the president enjoys consistently strong support among state Republicans whom Gardner must win over if he faces a primary challenge in 2020.
A poll released this week by Democratic firms Keating Research and OnSight Public Affairs found that an identical 39 percent of Colorado voters hold favorable views of Gardner and Trump.
The survey, which has a margin of error of 4.4 percentage points, found that 60 percent of Colorado voters view Trump unfavorably, while 43 percent hold unfavorable views of Gardner.
Gardner opposed Trump during the 2016 GOP primary. He eventually endorsed the businessman and former reality show star, but he quickly rescinded that support after a tape surfaced in which Trump bragged of sexually assaulting women. Gardner said he would instead write in the name of Mike Pence, Trump's vice president.
After 2016, however, Gardner became the head of the arm of the Republican Party that oversees Senate races. He helped engineer the party's strategy of clinging to Trump in conservative states, which helped the GOP gain two Senate seats while losing control of the House of Representatives in November.
Gardner voted for Trump's two Supreme Court nominees, the president's tax bill and the failed effort to repeal the Affordable Care Act.
"It shows just how out of step he is with Colorado," David Pourshoushtari, a spokesman for the Colorado Democratic Party, said in response to Gardner's endorsement of Trump. "Cory Gardner will face the consequences on Election Day 2020."