COMMON If one person slings mud or throws mud at another, they say bad things about them in an attempt to spoil their reputation. The elections have been straight personality contests, with the candidates slinging as much mud at their opponents as they can manage. The newspaper and magazine articles that followed were especially vicious, with supporters of both stars quick to throw mud. Note: You can describe this kind of behaviour as mud-slinging or mud-throwing. Labour and Tory chiefs have ordered an end to political mud-slinging. Note: These expressions are used to show disapproval.
fling (or sling or throw) mudmake disparaging or scandalous remarks or accusations. informal
The proverb throw dirt (or mud) enough, and some will stick , to which this phrase alludes, is attributed to the Florentine statesman Niccolò Machiavelli ( 1469–1527 ).