COUNCIL BLUFFS — An Omaha man pleaded guilty Tuesday in federal court to making threats against U.S. Sen. Joni Ernst.Robert W. Simet, 64, pleaded guilty in U.S. District Court of the Southern District of Iowa to one count of threatening to assault a United States official. Court documents show Simet believed the senator was involved with ISIS, and he told others last July that he might kill her at a Pacific Junction event at a motorcycle shop.