The Collaborative International Dictionary of English v.0.48:

Roorback \Roor"back\, Roorbach \Roor"bach\, n.
   A defamatory forgery or falsehood published for purposes of
   political intrigue. [U.S.]
   [1913 Webster]

   Note: The word originated in the election canvass of 1844,
         when such a forgery was published, to the detriment of
         James K. Polk, a candidate for President, purporting to
         be an extract from the "Travels of Baron Roorbach."
         [1913 Webster]

Moby Thesaurus II by Grady Ward, 1.0:

29 Moby Thesaurus words for "roorback":
   bruit, buzz, canard, character assassination, common talk, cry,
   dirty politics, flying rumor, grapevine, hearsay, idea afloat,
   last-minute lie, latrine rumor, muckraking, mudslinging,
   mudslinging campaign, news stirring, on-dit, political canard,
   report, rumble, rumor, scuttlebutt, smear campaign, talk,
   town talk, unconfirmed report, whisper, whispering campaign