Preckwinkle said in a statement Wednesday that she became aware of an allegation that Keller "had engaged in inappropriate behavior on his personal time."
Preckwinkle said that Keller did not deny the allegation. As a result, she asked for his immediate resignation.
Her full statement follows:
As President of the Cook County Board of Commissioners and as a woman, it is important to me to foster a workplace that is respectful, where all people are treated with dignity. I have always had zero tolerance for inappropriate and disrespectful behavior. On Friday, I became aware of an allegation that my Chief of Staff, John Keller, had engaged in inappropriate behavior on his personal time. The allegation was corroborated. I confronted Mr. Keller; he did not deny the allegation. Yesterday, I demanded and received his immediate resignation.