Agent astroturfeur 

Person who mischievously promotes division in another organisation (generally political) by creating the impression of grassroots support for a contender for a leadership position. See astroturf.

After the Blue Party flopped in the elections, Diane Ale blogged that support for Squirrel Nutkin for leader was growing. She's such an an agent astroturfeur.

Agent astroturfeur by Gus Friar May 18, 2007