Rankin ran for office more than a dozen times before being elected to the Vancouver City Council in 1966 as the sole independent alderman on a council dominated by the conservative Non-Partisan Association. Vancouver's aldermen were elected through an "at large" system rather than by ward meaning voters from wealthier neighbourhoods were able to monopolise council elections and that only candidates who could afford a citywide campaign had a chance of being elected. Rankin helped form the Committee of Progressive Electors (COPE) as a left wing civic political party and it subsequently pushed for a ward-based electoral system to be introduced in Vancouver, culminating in a referendum in October 1973, at which the ward proposal was defeated.