CHICAGO (AP) — Former Illinois House Speaker Michael Madigan, the Chicago Democrat who served in the post for decades, has resigned as state party chairman.

Cook County Clerk Karen Yarbrough will be appointed as interim leader of state Democrats until a permanent replacement is named.

Madigan on Monday did not give a reason for resigning as party chairman, a post he’s held since 1998. He did say he has been the target of attacks by people seeking to diminish his achievements.

Madigan has been tarnished by a federal bribery investigation announced last summer. He resigned from the Legislature on Thursday. Jockeying to be Madigan’s permanent successor has begun, with 2nd District Congresswoman Robin Kelly announcing plans to seek the chairmanship.