For a second time in eight days, Sen. Bernie Sanders apologized to women on his 2016 presidential campaign, as he seeks to put behind him a series of damaging reports about the mistreatment of female staff members that threatens to undercut another likely White House bid.

“It appears that as part of our campaign, there were some women who were harassed and mistreated,” Sanders said during a scheduled news conference Thursday about prescription drugs. “I thank them from the bottom of my heart for speaking out. What they experienced was absolutely unacceptable and certainly not what a progressive campaign or any campaign should be about.”

“When we talk about — and I do all the time — ending sexism and all forms of discrimination, those beliefs cannot just be words. They must be based in day-to-day reality and the work we do, and that was clearly not the case in the 2016 campaign.”

His apology follows several recent articles describing harassment, sexism and gender discrimination in Sanders’ 2016 campaign, including a report last week by The New York Times and another Wednesday night by Politico. Several of his top aides and advisers have been implicated, and Jeff Weaver, his campaign manager, has said he would not return in the same role if Sanders runs again.

Some campaign alumni have requested a meeting with the senator and his campaign leadership team to discuss the treatment of women going forward, with some delegates suggesting he should not run again until he addresses the issue of sexism in his campaign.

In a statement posted on Twitter shortly after Thursday’s news conference, Sanders said: “Clearly we need a cultural revolution in this country to change workplace attitudes and behavior. I intend in every way to be actively involved in that process.”

Though Sanders has not yet announced he is running for president, allegations of harassment, sexism and gender discrimination that have emerged in recent weeks have already threatened to impede a potential 2020 bid.

In the Times article, former staff members described in on-the-record interviews their experiences with sexism, including harassment and pay inequity. They portrayed the insurgent 2016 campaign as disorganized and decentralized, making it hard to report mistreatment.

In an interview on CNN last week following the Times report, Sanders said he was proud of his 2016 campaign and attributed any missteps with staff members to the explosive growth that was sometimes overwhelming.

“I certainly apologize to any woman who felt she was not treated appropriately, and of course if I run we will do better the next time,” he said.

As Sanders considers his next steps, he has faced criticism for seemingly surrounding himself with many of the same people who worked on his last campaign, stoking anxiety that little would change should he run again.