I would say that one of President Kennedy's most borrowed element from his legacy is the idea of self- sacrifice.  A part of his political legacy has been this idea that the definition of American greatness lies in the notion of individuals sacrificing for something larger than themselves.  This is evoked in his notion of "Ask not what your country can do for you" sentiment in his inaugural address, but was also seen in his administration.  His ability to inspire Americans to see space as a frontier worthy of exploration was one in which there had to be a sense of self- sacrifice for the ideal of the space frontier.  The advent and expansion of the Peace Corps was something heavily reflective of the Kennedy ideal of a "Pax Americana" in which Americans were not afraid to help others in need.  Even his idea of Civil Rights legislation was one in which Americans would have to sacrifice their notion of a segregated America into a vision whereby integration would be a reality that could not be denied in public and private realms.  The idea of self- sacrifice becomes an essential part of President Kennedy's political legacy.