Harris was elected leader of the Green Party of Canada on 14 February 2003, defeating Jason Crummey and John Grogan with over 81% of the votes cast by delegates. He replaced interim leader Chris Bradshaw, who led the party from 2001 to 2003. In his campaign for the leadership, Harris asked the membership to elect his preferred slate of council candidates. Other than leadership contestants, council candidates were not given the membership list to use in their campaign despite the green party constitution clearly offering them that right.