A concentrated and prolonged effort to damage or ruin someone's or some group's reputation through the perpetuation of claims about their failures or faults, whether these are true, exaggerated, or falsified. Generally as a means of persuading a large number of people against him, her, or them, especially in a political election. Primarily heard in US. The local sheriff's slim lead heading into the election quickly evaporated after a vicious smear campaign began targeting his former substance abuse. I think we need to start a smear campaign to slow down the competitor's growth in the market, but no one can know that it's coming from us!