David Brock abruptly announced on Wednesday that he will be giving up his role as chairman of the far-left organization Media Matters for America.

Both Brock and Media Matters made the announcement via Twitter while providing no further explanation as to why he has suddenly exited the anti-conservative attack organization he founded in 2004.

Brock tweeted on Wednesday:

As of today, I am leaving my roles as Chairman of the board of Media Matters for America, Media Matters Action Network, and American Bridge. It’s been my great honor to work with such talented and committed teams over the last 20 yrs. I’ll be sharing more about my next steps soon.

Brock shared a statement from American Bridge co-founder Bradley Beychok praising him as a “visionary who reshaped the landscape of the Democratic ecosystem.” The statement read:

From its inception, Bridge has been doing the work of holding Republicans accountable – not just in election years, but all of the time. This organization has found a way to weaponize research and tracking tools to build narratives and win elections with remarkable effectiveness. That would not have been possible without David’s leadership. David has always found a way to have an important impact – we expect no less from him in the future and wish him success.

Likewise, Media Matters for America released a statement of its own declaring that Angelo Carusone would be taking Brock’s place as Chairman. The organization said via Twitter:

Media Matters would not exist without David Brock’s vision and know-how. We appreciate his intuition and laying the groundwork for the organization nearly 20 years ago as well as his guidance as Media Matters has expanded and increased its mission effectiveness over the years. We thank David for his efforts and wish him success as he begins a new chapter.

David Brock initially earned a name for himself as a conservative investigative journalist in the early-1990s with the release of his book The Real Anita Hill in response to the tumultuous confirmation hearing of conservative Justice Clarence Thomas to the Supreme Court. Brock later denounced the claims he made in the book and became an advocate for the Clinton dynasty in the late 1990s. His 2002 memoir, Blinded by the Right, received mixed reactions from liberal critics who felt it came across less as a tell-all confessional and more as a shrewd grift to ingratiate himself with his new fanbase. In his review for The Nation, famed liberal author Christopher Hitchens derided Brock’s book as “an exercise in self-love, disguised as an exercise in self-abnegation.”

“I wanted to take an extra shower after trudging through this dismally written, pick-nose, spiteful and furtive little book. It glitters with malice and the more cowardly kind of “disclosure”; it’s a dank, filthy tissue turned inside out,” wrote Hitchens.