Manchurian candidate

Etymology
From the title of the 1959 novel or 1962 film , in which the son of a prominent US political family is brainwashed into being an unwitting assassin for a communist conspiracy.

Also comes from the infamous Japanese puppet state of Manchukuo during World War II.

Noun

 * 1) A person, especially a politician, who has unknowingly been convinced to act to benefit some interest.