1
general::
Phrase(s): a smear campaign (against someone)
a campaign aimed at damaging someone’s reputation by making accusations and spreading rumors. • The politician’s opponents are engaging in a smear campaign against him. • Jack started a smear campaign against Tom so that Tom wouldn’t get the manager’s job.
McGrawhill's American Idioms And Phrasal Verbs
2
general::
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."
American Heritage Idioms