President Barack Obama, with his blazer slung over his shoulder, walks over to wish Air Force members and their families a Happy Fourth of July, at Andrews Air Force Base, Md., Friday, July 2, 2010, before boarding Marine One for a trip to Camp David, Md. At left is White House photographer Pete Souza. (AP Photo/Charles Dharapak)

Photo by: Charles Dharapak

President Barack Obama, with his blazer slung over his shoulder, walks over to wish Air Force members and their families a Happy Fourth of July, at Andrews Air Force Base, Md., Friday, July 2, 2010, before boarding Marine One for a trip to Camp David, Md. At left is White House photographer Pete Souza. (AP Photo/Charles Dharapak)