President Obama greets well-wishers after stepping off Air Force One upon his arrival at the Detroit Metropolitan Wayne County Airport in Romulus, Mich., on Monday, Dec. 10, 2012, before going to the Daimler Detroit Diesel plant in Redford. (AP Photo/Charles Dharapak)

Photo by: Charles Dharapak

President Obama greets well-wishers after stepping off Air Force One upon his arrival at the Detroit Metropolitan Wayne County Airport in Romulus, Mich., on Monday, Dec. 10, 2012, before going to the Daimler Detroit Diesel plant in Redford. (AP Photo/Charles Dharapak)