ideologist

from WordNet (r) 3.0 (2006)

ideologist
    n 1: an advocate of some ideology [syn: {ideologist},
         {ideologue}]

from The Collaborative International Dictionary of English v.0.48

Ideologist \I`de*ol"o*gist\, n.
   1. One who treats of ideas; one who theorizes or idealizes;
      one versed in the science of ideas, or who advocates the
      doctrines of ideology.

   2. An ideologue.
      [PJC]