US President Barack Obama (C) walks to his bus as he arrives in Minneapolis-St. Paul International Airport, Minnesota, August 15, 2011, where he is to begin his three-day bus tour in the Midwest centering on ways to grow the economy. AFP PHOTO/Jim WATSON (Photo credit should read JIM WATSON/AFP/Getty Images)
US President Barack Obama (C) walks to his bus as he arrives in Minneapolis-St. Paul International Airport, Minnesota, August 15, 2011, where he is to begin his three-day bus tour in the Midwest centering on ways to grow the economy. AFP PHOTO/Jim WATSON (Photo credit should read JIM WATSON/AFP/Getty Images)
US President Barack Obama (C) walks to his bus as he arrives in Minneapolis-St. Paul International Airport, Minnesota, August 15, 2011, where he is to begin his three-day bus tour in the Midwest centering on ways to grow the economy. AFP PHOTO/Jim WATSON (Photo credit should read JIM WATSON/AFP/Getty Images)
Secret Service stand watch next to US President Barack Obama's bus as he visits with people at the Coffee Mill in Zumbrota, Minnesota, August 15, 2011 during his three-day bus tour in the Midwest centering on ways to grow the economy. AFP PHOTO/Jim WATSON (Photo credit should read JIM WATSON/AFP/Getty Images)
President Barack Obama waves before boarding his bus after having lunch and greeting people at The Old Market Deli, Monday, Aug. 15, 2011, in Cannon Falls, Minn., during his three-day economic bus tour. (AP Photo/Carolyn Kaster)
President Barack Obama's bus drives among corn fields, Monday, Aug. 15, 2011, as it approaches Decorah, Iowa, during a three-day economic bus tour. (AP Photo/Carolyn Kaster)
