Mourners create a memorial at the fountain of the Aurora Municipal Center after a prayer vigil Sunday for the 12 victims of Friday's mass shooting at the Century 16 movie theater. Kevork Djansezian/Getty Images hide caption

itoggle caption Kevork Djansezian/Getty Images

Mitt Romney speaks at a campaign stop in Roxbury, Mass., on Thursday. Evan Vucci/AP hide caption

itoggle caption Evan Vucci/AP

GOP presidential candidate Mitt Romney speaks at a campaign rally in Bowling Green, Ohio, on Wednesday. J.D. Pooley/Getty Images hide caption

itoggle caption J.D. Pooley/Getty Images

President Obama clasps hands with Sen. Mark Warner (left), D-Va., and Democratic Senate candidate Tim Kaine during a campaign stop Friday in Virginia Beach, Va. Susan Walsh/AP hide caption

itoggle caption Susan Walsh/AP