By your standards, we've probably never had such a thing. Look back to the election 1800: does this sound like a clean campaign to you? http://en.wikipedia.org/wiki/Election_of_1800#Campaign

What you're specifically alleging could be equally applied to elections in which Nixon was involved, which wer influenced by McCarthyism, when J Edgar Hoover was in office...we could go on tracing it back to the suppression of Shays' Rebellion in 1787 (see http://en.wikipedia.org/wiki/Shay%27s_Rebellion#Impact_on_Co...).

http://en.wikipedia.org/wiki/Election_of_1800#Campaign