smear campaign

noun

1. a campaign to tarnish the reputation of a public figure, especially by vilification or innuendo.

Idioms and Phrases

An attempt to ruin a reputation by slander or vilification, as in This press agent is well known for starting smear campaigns against her clients' major competitors. This phrase was first recorded in 1938 and uses smear in the sense of “an attempt to discredit” or “slander.”