Democratic Sen. Tammy Duckworth is wading into the open primary to succeed longtime Sen. Dick Durbin, endorsing Lt. Gov. Juliana Stratton to join her in representing Illinois in the Senate.

Juliana Stratton, who has served as Illinois’ lieutenant governor, has been public about her interest in Dick Durbin’s seat.

Dick Durbin, the longtime second-ranking Democrat in the Senate, announced plans to retire at the end of next year, setting off a succession scramble to take his powerful leadership spot in the chamber and a likely crowded primary in Illinois for the seat.