David Brock, founder of the left-leaning Media Matters for America non-profit and a longtime Hillary Clinton ally, suffered a heart attack on Tuesday, according to a press release.

"David Brock suffered a heart attack while working in the Washington DC office early Tuesday," the release said on Wednesday.

It added that he was quickly treated and stabilized.

"He was quickly transported to a local hospital, received prompt medical treatment, and we are looking forward to a swift recovery," the release said.

Brock is a former conservative journalist who now heads a network of liberal nonprofits aimed at combating Republicans and conservative media.