He was previously president of the Quebec Liberal Party, and was also the party's candidate in Rivière-du-Loup for the 1994 and 2007 provincial elections. He faced some controversy during the campaign, as he was arrested for impaired driving on 24 September 2008, and pled guilty on 19 December. His driver's license was suspended for one year.
He has also faced allegations that he violated provincial ethics laws by lobbying the municipal government of Rivière-du-Loup less than two years after leaving office. Premier Jean Charest stood behind D'Amour, however, crediting him with being honest and forthcoming with the voters about his mistakes. He resigned the Liberal caucus to sit as an independent on 10 November 2009, following revelations that he was under investigation for allegedly accepting an envelope of money from a developer on behalf of Michel Morin, his successor as mayor of Rivière-du-Loup.
An investigation by the province's chief electoral officer cleared him of wrongdoing, and he was subsequently readmitted to the Liberal caucus on 24 December.