The Collaborative International Dictionary of English v.0.48:

spin doctor \spin doctor\ n.
   a spokesperson for a political party or candidate who tries
   to forestall negative publicity.
   [WordNet 1.5] spin drier

WordNet (r) 3.0 (2006):

spin doctor
    n 1: a public relations person who tries to forestall negative
         publicity by publicizing a favorable interpretation of the
         words or actions of a company or political party or famous
         person; "his title is Director of Communications but he is
         just a spin doctor" [syn: spin doctor, spinmeister]