Former Rep. Debbie Halvorson (D-Ill.) on Monday became the first formal candidate for Jesse Jackson Jr.’s congressional seat, but a wide and diverse slate of contenders are expected to announce bids in the coming days.

Jackson (D-Ill.) announced his resignation last week, citing health problems. Gov. Pat Quinn (D) has set a special primary election for Feb. 26 and a general election for March 19, although he’s trying to get the court to allow him to push that date back to April 9, when there are municipal elections already scheduled.