Progressive billionaire Tom Steyer has been vocal in his calls to “abolish ICE” to California voters, even though he previously invested nearly $90 million in a company that operates the state’s largest immigration detention center.

Despite efforts to dismiss these criticisms, Steyer recently addressed the issue in an interview with the Sacramento Bee, acknowledging it as a “mistake.”

“We were never involved in managing the company,” Steyer explained. “However, it was an error to think that investing in that area was acceptable.”

Back in 1986, Steyer established Farallon Capital Management, a hedge fund that, under his leadership, invested in CoreCivic, a company that manages private prisons. At its peak, Farallon’s stake in CoreCivic was valued at $89.1 million.

Currently, CoreCivic operates five facilities in California, according to its website, with at least two housing individuals detained by federal immigration authorities—one located near San Diego and another in Kern County.

Steyer departed from Farallon and divested his interest in the hedge fund in 2012.

The candidate’s ties to CoreCivic are coming under increased scrutiny by the left. After the implosion of U.S. Rep. Eric Swalwell’s campaign this weekend, Steyer is now one of two leading Democratic competitors set to swoop up most of Swalwell’s voters and surge in the polls.

Steyer has framed his regret being involved with CoreCivic as a wake-up call that led him to walk away from the hedge fund industry. He said it also led to his work advocating against mass incarceration.

“It was also a big wake-up call that I was in the wrong place, that I was in a business that was taking me to places I absolutely didn’t want to go,” Steyer said at a March town hall. “And there’s a reason I walked away from that business and walked away from a ton of money.”

Candidates aren’t letting up on their attacks against Steyer as they attempt to link him with ICE.

“Before he was a progressive, he made millions off of companies that operate ICE detention centers, that operate private prisons that incarcerated young children,” state Superintendent of Public Instruction Tony Thurmond said in an interview with an influencer late March.

Ads have bombarded televisions highlighting his link. The billionaire has aired ads trying to tell viewers that those other ads are false, Politico reported.

“Those investments were 20 years ago, and I left my firm over a decade ago and pledged most of my earnings to charity,” Steyer said in his hitback.

Regardless, Steyer is still seeing momentum. A poll dropped Tuesday, conducted April 8 to 10, showed him leading the entire field at 21%.