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.It was as a lifelong broadcaster that Mike Huckabee, the onetime "pastor on TV," perfected the conservative amiability that helped him win the Iowa caucuses in 2008 and could again set him apart from an increasingly crowded field of Republicans. But in the GOP of 2016, when the sharp edge plays better than the soft smile, Huckabee enters the race facing a key question: Will the same "I''m not mad at anybody" on-air vibe that fueled his rise make him a non-starter for mad-as-hell early Republican voters?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.