whispering campaign

American  

noun

1. the organized spreading of insinuations or rumors to destroy the reputation of a person, organization, etc.

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whispering campaign British  

noun

1. the organized diffusion by word of mouth of defamatory rumours designed to discredit a person, group, etc

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whispering campaign Idioms  

1. A deliberate spreading of derogatory rumors about a candidate, as in That whispering campaign destroyed his chances for election. [c. 1920]

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Etymology

Origin of whispering campaign

First recorded in 1915–20