SPRINGFIELD — In a letter to U.S. Rep. John Shimkus, Illinois’ two U.S. senators raised concerns about Gov. Bruce Rauner’s administration participating in a call to discuss the process of nominating federal judges, U.S. attorneys and U.S. marshals.The letter was sent Tuesday to Shimkus, a Republican from Illinois, by U.S. Sens. Richard J. Durbin and Tammy Duckworth, both Democrats.The senators wrote that the letter was a follow-up to a Jan. 17 phone conversation.A Rauner representative — Kathy Lydon …