In political jargon, a useful idiot is a person perceived as a propagandist for a cause whose goals they are not fully aware of, and who is used cynically by the leaders of the cause.
The phrase is often attributed to Lenin in the West. However, in a 1987 article, American journalist William Safire noted that a Library of Congress librarian had not been able to find the phrase in Lenin's works. The book They Never Said It also suggests the attribution is false.
In the Russian language, the equivalent term "useful fools" (Russian: полезные дураки, tr. polezniye duraki) was already in use in 1941. It was mockingly used against Russian "nihilists" of 1860s who, for Polish agents, were said to be no more than "useful fools and silly enthusiasts".
This term (singular: полезный дурак, tr. polezni durak) was attributed to Lenin by some Russian writers, e.g., by Vladimir Bukovsky (1984).
In the memoir of actor Alexander Granach, the phrase was used in the description of a boyhood incident in a shtetl in Western Ukraine.
In 1948 (June), New York Times used the term in an article on contemporary Italian politics, citing the social-democratic Italian paper L'Umanità.
In 1958 (January), Time magazine started to use the phrase.
In 1959, the Economic Research Council's journal Economic Digest not only mentions the phrase but attributes it to Lenin.
In 1961, the term appears in an American magazine when referring to Jean-Paul Sartre.