OK I know my ignorance is showing BUT, why is Duke University so liberal ?
It's easy to understand the North Eastern schools but Duke ?
Just hazarding a guess here, but that entire Raleigh/Durham/Chapel Hill area of NC is otherwise infested with liberals. Duke and other universities in that region bring a lot of them (most universities are themselves infested with liberals since that's what they do -- crank out more liberals), but Research Triangle Park attracts a lot of them too since it's become very much a mecca for corporations in regulated industry (pharma, med devices, contract research organizations, etc.).
I've done some research on NC, considering it as a possible retirement location. When you start going rural, it starts getting more and more red, but the blues have their hooks pretty firmly in the NC cities/built-up areas.