Mike Johnston, a Western Slope-born former state senator, wants to be the Democrat who unseats Republican U.S. Sen. Cory Gardner in 2020.

“I think one of the things that gives me a real advantage is people are looking for someone who represents Colorado,” Johnston told The Denver Post in announcing his run. “I’m a fluent Spanish speaker, and I’ve had a diverse set of experiences and jobs in all parts of Colorado.”

The 44-year-old father of three joins a growing list of Democrats competing for the chance to challenge Gardner in what is expected to be one of the most high profile and contentious Senate races in the country in 2020. Gardner, a first-term senator, is the only Republican to win a Senate, gubernatorial or presidential race in Colorado since 2008.

So far, three other Democrats have announced: Lorena Garcia of Denver, Trish Zornio of Superior and Keith Pottratz of Grand Junction.

Johnston is familiar with the high-wire act that comes with a large and competitive primary. He came in third place in the 2018 Democratic gubernatorial primary.

He said the experience gave him connections throughout the state and to major donors nationwide, which will be essential in challenging Gardner. The Republican has been making national connections of his own, raising money for the party all over the country as chair of the National Republican Senatorial Committee.

Johnston raised about $2.5 million in standard campaign contributions during the primary last year, and his PAC raked in another $7.7 million, according to campaign finance records submitted to the Colorado Secretary of State’s Office. A large chunk of that money came from gun-control advocates like Michael Bloomberg, and Johnston said he won’t shy away from raising the issue of gun laws during the campaign.

The 2013 Colorado bills limiting ammunition magazines to 15 rounds and requiring universal background checks are some of the laws he’s most proud of helping pass, he said.

At the top of that list, though, is the ASSET bill, which gives in-state tuition to college students who don’t have documentation to live in the United States legally.

The idea for the bill came to him while he was a principal at Mapleton Expeditionary School of the Arts in Thornton, he said. He encountered dozens of students who couldn’t afford a Colorado college because their parents brought them into the country illegally.

But the education bill Johnston is best known for — especially among Colorado educators — is a 2010 bill that tied teachers’ evaluations to their students’ academic growth and weakened teacher tenure protections after two consecutive years of unsatisfactory evaluations.

Two influential teachers unions endorsed Cary Kennedy in Colorado’s Democratic primary for governor in part because of Johnston’s ties to the education reform community.

“Colorado deserves a senator that’s willing to run at Colorado’s toughest problems,” Johnston said, listing off additional topics including climate change, immigration and access to public lands. “Cory Gardner claims to be independent when he campaigns in Colorado, but he votes with (President Donald Trump) 92 percent of the time.”

Former state Treasurer Walker Stapleton, who lost to Gov. Jared Polis in November, knows first hand how challenging it is to run as a Republican in Colorado with Trump in the White House, but he said he wouldn’t write Gardner’s political obituary yet.

“One of his many skills and traits is that he’s a fantastic retail politician,” Stapleton said. “He’s ready and prepared to run a race on his own terms as his own person.”

Gardner has broken with the White House on several occasions, Stapleton added — even holding up the president’s nominees for the Department of Justice over marijuana policy.