Even as a rival says he is 'declining,' Biden keeps poll lead

Former vice president Joe Biden continues to hold a lead among Democratic presidential aspirants, a new poll showed Sunday, despite recent questions about his age and mental clarity.Biden's lead among Democratic voters has remained relatively steady, as he and senators Bernie Sanders and Elizabeth Warren increasingly emerge as a distinct top tier in the large field, according to the Washington Post/ABC News poll.The poll showed Biden favored by 29 percent of registered Democrats or Democratic-le