A useful idiot is someone who supports one side of an ideological debate but who is manipulated and held in contempt by the leaders of their faction. The term originated in early 1950s America, in reference to members of the Socialist Party, allegedly promoted by the malevolent Russian KGB to weaken America as a nation.
As a subjective label, the term is often abused. There are reasonable differences on matters of rhetoric and tactics in any ideological movement, but these differences can be unjustly smeared as idiocy with this label. Nor are all poor representatives of a position necessarily useful idiots: a useful idiot is specifically a poor representative who is raised as a figurehead by a third party with malign intentions. VenomFangX might be a spectacular failure at Christian apologetics, but he's not a useful idiot because his popularity derives from other Christians, not atheists.
 Alleged examples
- S.E. Cupp - The atheist who hates atheists. She is frequently considered a useful idiot of the religious right, as an atheist who talks in detail about how atheists are sexist or evil or silly or unreasonable.
- David Frum - A conservative American blogger, he is thought by many on the left to be "the reasonable one" and many on the right to be a useful idiot of liberals.
- Kent Hovind - A creationist and evangelist with a diploma-mill doctorate and a 10-year jail sentence, his tactics were met with scorn by more respectable creationist agencies like Answers in Genesis, who considered him well-meaning but a useful idiot for the villainous Darwinists.