John Walsh, the former U.S. attorney for Colorado, on Tuesday announced he’s joining the crowded Democratic primary for the U.S. Senate seat held by Republican U.S. Sen. Cory Gardner.

Calling himself a “pragmatic progressive leader,” the 57-year-old attorney said in an interview that his career “working on really complex, difficult problems and finding solutions for the people of Colorado” sets him apart in a primary field that has grown into double digits.

Walsh joins nine other Democrats in the 2020 race, including former state Sen. Mike Johnston, former House Speaker Andrew Romanoff and former congressional candidate Stephany Rose Spaulding.

Late Monday, former ambassador Dan Baer – who directed the Colorado Department of Higher Education under Gov. John Hickenlooper and briefly ran for Congress two years ago – announced he was also running for Gardner’s seat.

“Our state deserves better than what we’re getting from Donald Trump and Cory Gardner; we deserve representation that fights for the families of our state,” Walsh said Monday.

“But Cory Gardner only seems to care about the bottom lines of big banks, insurance companies and Washington special interests. I’ve spent my whole life fighting against institutions and individuals who have tried to get in the way of an open and fair system for all.”

WATCH a Walsh campaign video below.

Walsh served for six years as Colorado’s chief federal law enforcement officer under President Barack Obama, guiding the federal government’s relationship to the state as Colorado established a legal recreational marijuana industry.

As chair of the Attorney General’s Advisory Committee of U.S. Attorneys, Walsh said he led the federal effort to “hold the big banks responsible for their misconduct in the financial crisis,” leading to the imposition of tens of billions of dollars in penalties on banks, including a record $7 billion penalty against Citibank for its conduct in Colorado.

In addition, he said he played a key role in the administration’s efforts to pass federal sentencing reform and take on pharmaceutical firms and distributors who contributed to the opioid crisis.

“I think that that background – working on issues and establishing a strong progressive record and actually making progress on those issues – is what Coloradans are looking for,” Walsh said. “They’re looking for a fierce advocate in the U.S. Senate on their behalf, and I think I bring that.”

Walsh was harshly critical of Gardner’s votes to repeal the Affordable Care Act and to side with Trump on the president’s declaration of a national emergency on the southern border.

“For whatever reason, Cory Gardner paid attention to the president and failed to comply with what I would say is a constitutional obligation,” Walsh said.

“One of the most troubling things about the way Cory Gardner has acted as U.S. senator is that, for two full years, while all of this has been going on and there were obvious overreaches and abuses of power by President Trump, other than a few tweets, Cory Gardner did nothing – did nothing to ensure that our constitutional system operated the way that our founders intended it to.”

He added: “That’s crucially important to the constitutional balance of power and one of the things I feel fervently about. It’s part of the political crisis that this country is suffering at the moment, and I think Cory Gardner has aided and abetted the problem by not taking more action to hold the president accountable.”

Next year’s Colorado Senate race has drawn an unusually high number of challengers, in part because Gardner is one of only two GOP incumbent senators running in states won by Democrat Hillary Clinton, who carried Colorado by 5 percentage points.

Other Democrats in the race are scientist and educator Trish Zornio, community organizer Lorena Garcia, pharmacist Dustin Leitzel, veterans advocate Keith Pottratz, and climate activist Diana Bray.

State Sen. Kerry Donovan of Vail and former Boulder County Democratic chair Ellen Burns are considering joining the field, and U.S. Reps. Ed Perlmutter and Joe Neguse are said to be mulling bids.

Walsh ran for Denver district attorney in 2004 but lost in a Democratic primary to Mitch Morrissey, who went on to serve as Denver’s DA for three terms.

A month ago, Walsh stepped down from the Denver office of international law firm WimerHale, where he had been a partner since leaving the Obama administration in 2017.

Walsh and a team of the firm’s attorneys were honored Friday with the Rocky Mountain Immigrant Advocacy Network’s 2019 Pro Bono Service Award for their work representing immigrant parents and relatives detained and separated from their children under the Trump administration’s family separation policy.

Walsh lives in Denver’s Park Hill neighborhood with his wife, Lisa Christian, a former federal prosecutor who works at a wind energy company. They have three grown children.