fling/sling/throw mud

sling mud

or

throw mud

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.
See also: mud, sling

fling (or sling or throw) mud

make 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 ).
See also: fling, mud

fling/sling/throw ˈmud (at somebody)

(informal) try to damage somebody’s reputation by telling other people bad things about them: Just before an election, politicians really start to sling mud at each other. ▶ ˈmud-slinging noun: There’s too much mud-slinging by irresponsible journalists.
See also: fling, mud, sling, throw