According to About.com's Steve Smith, the nickname "Tricky Dick" for Richard Nixon, the 37th President of the United States, was a response to smear campaign he ran against Helen Douglas when both were competing for a Senate seat in 1950. He was first referred to as "Tricky Dick" in a 1950 newspaper campaign funded by a Democratic committee urging citizens to “Look at Tricky Dick Nixon’s Republican Record.”
Nixon, who had served on the House Un-American Activities Commission (HUAC), attempted to link Douglas to communism, even going as far as to print anti-Douglas leaflets on pink paper ("pink" being a term for Americans with loose ties to "red" Communist sentiments). In response, a committee supporting Douglas ran several full-page newspaper ads showing a cartoon Nixon baling hay labeled "Campaign Trickery" into a donkey labeled "Democrat."
Nixon served as president from 1969 to 1974. He is the only president to resign from office, which he did following his implication in the Watergate scandal. It is a common misconception that the nickname "Tricky Dick" hails from the Watergate period; it originated decades earlier. The name stayed with him throughout his political career and endures in post-presidential references to the controversial public figure.