WordNet (r) 3.0 (2006):

muckraking
    n 1: the exposure of scandal (especially about public figures)

Moby Thesaurus II by Grady Ward, 1.0:

21 Moby Thesaurus words for "muckraking":
   attack, blackening, character assassination, defamation,
   defamation of character, defilement, denigration, dirty politics,
   last-minute lie, malicious defamation, mudslinging,
   mudslinging campaign, name-calling, political canard, revilement,
   roorback, smear, smear campaign, smear word, vilification,
   whispering campaign