often (not ALL the time) vice presidents are picked because they hold a valuable constituent base for the candidate that he would have trouble garnering on his own. The point is that Powell represents a portion of America that Obama would have a hard time reaching. If Obama is seen as Jr statemen with little experience the addition of someone like Powell who has vast amounts of foreign policy stuff under his belt, would easily counter McCain's military experience. Just my thoughts, Its a theory I am probably wrong