Presidential candidates are a breed apart, often propelled by traits that have shaped their careers and have deep roots in personal histories.Often their greatest strength can turn at supernova speed into their greatest weakness. The exact qualities that set them apart from the field trip them up eventually over the long haul of a presidential campaign.Some see former Texas governor Rick Perry as one of the most instinctive retail politicians in the 2016 GOP field. Others see a glib pitchman who must overcome the perception that he''s all flash and little substance. Four years after his famous ''oops'' incident, can he persuade voters that he''s the real deal?In this series of eBooks, The Washington Post is exploring in-depth all these key characteristics of the leading presidential contenders, the very characteristics that could help make one of them the country''s next commander in chief—or forever sink their presidential ambitions.