Wisconsin Gov. Scott Walker offers cheese and ice cream to guests in his hospitality room at the Iowa Lincoln Day Dinner in Des Moines on Saturday. Charlie Neibergall/AP hide caption

itoggle caption Charlie Neibergall/AP

Former Florida Gov. Jeb Bush had a tough week with his changing positions on the Iraq War and trying to explain whether he would have authorized it, knowing what we know now. Ross D. Franklin/AP hide caption

itoggle caption Ross D. Franklin/AP

Republican presidential hopeful Sen. Marco Rubio, R-Fla., speaks Wednesday before the Council on Foreign Relations in New York, where he laid out his "Rubio Doctrine." Mary Altaffer/AP hide caption

itoggle caption Mary Altaffer/AP

In an interview with NPR's Morning Edition host Steve Inskeep, President Obama said Wisconsin Gov. Scott Walker is advocating a "foolish approach" to Iran and that he should "bone up on foreign policy." Mito Habe-Evans/NPR hide caption

itoggle caption Mito Habe-Evans/NPR