The Collaborative International Dictionary of English v.0.48:

Demagog \Dem"a*gog\ (?; 115), n.
   Demagogue. Demagogic

WordNet (r) 3.0 (2006):

demagog
    n 1: a political leader who seeks support by appealing to
         popular passions and prejudices [syn: demagogue,
         demagog, rabble-rouser]