Residents of city and suburban neighbourhoods have diverged in the way they vote, with inner-city dwellers preferring political parties on the left while suburbanites increasingly vote for parties on the right. Yet it is not clear whether such a division is more evident between residents of central and suburban municipalities (the jurisdictional hypothesis), or between residents of neighbourhoods differentiated by urban form and, by assumption, lifestyle (the morphological hypothesis). While there are clear reasons for the predominant reliance on municipal differences in research based in the U.S. and other countries, it is not evident that these reasons apply in the Canadian context. This article examines how urban boundaries articulate electoral differences between metropolitan residents in Canada’s three largest urban regions, using aggregate election data for federal elections between 1945 and 2000, survey data from the 2000 Canada election study and a series of indices developed by the author. It is found that while trends towards city–suburban polarization are similar regardless of the boundaries used to define the zones, in the
Canadian case the results are stronger and more significant when boundaries based on urban form (between pre-and post-war development) are employed. The implications of these results for the relationship between urban space and political values in Canadian cities are then discussed.