President Barack Obama attends a campaign event at the Nelson Pioneer Farm & Museum, Tuesday, Aug. 14, 2012, in Oskaloosa, Iowa, during a three-day campaign bus tour through Iowa. (AP Photo/Carolyn Kaster)

Photo by: Carolyn Kaster

President Barack Obama attends a campaign event at the Nelson Pioneer Farm & Museum, Tuesday, Aug. 14, 2012, in Oskaloosa, Iowa, during a three-day campaign bus tour through Iowa. (AP Photo/Carolyn Kaster)