President Obama walks on stage after being introduced by first lady Michelle Obama (not shown) during his final 2012 campaign event in downtown Des Moines, Iowa, Monday, Nov. 5, 2012. (AP Photo/Pablo Martinez Monsivais)

Photo by: Pablo Martinez Monsivais

President Obama walks on stage after being introduced by first lady Michelle Obama (not shown) during his final 2012 campaign event in downtown Des Moines, Iowa, Monday, Nov. 5, 2012. (AP Photo/Pablo Martinez Monsivais)