Useful Idiot (more from Wikipedia)

"In political jargon, the term "useful idiot" was used during the Cold War by certain anticommunists to describe communists in western countries (particularly in the United States). The implication of the insult was that the communist in question was naive, and that he or she was being cynically used by the Soviet Union or another Communist state, thus unwittingly being a traitor to his or her home country.

The term is sometimes claimed to have been coined by Vladimir Lenin to describe those western reporters and travellers who would endorse the Soviet Union and its policies in the West. This story is apocryphal, since no reference to a communist being called a "useful idiot" was made in the United States until 1948, and not until decades later would the attempts to attribute the phrase to Lenin be made. Lenin never wrote it in any published document, no one has ever claimed to have heard him say it, and it also contradicts almost every document Lenin wrote and every speech he made in reference to the Comintern."