Rep. Jerry Costello’s retirement at the end of this Congress has led a number of ambitious Illinois politicos to eye the Democrat’s 12th district seat.

Jason Plummer, who was the 2010 GOP nominee for lieutenant governor, entered the race earlier this week, joining three other Republicans in the field. And the St. Louis Post-Dispatch reported that Madison County Chief Judge Ann Callis (D) is likely to make a bid for the seat.

If Callis jumps in the race, national Democrats would consider her a top-tier candidate.