National elections in Canada are really 338 simultaneous elections held across the country at the same time. This is an increase in 30 seats across the nation since the last election. In addition to the new seats, most electoral boundaries have been re-drawn and 31 districts were renamed.

The old and new boundaries can be compared at Elections Canada in a scalable online map. You can also view & download electoral district maps from Elections Canada.

Perhaps the most interesting ridings in any election are the marginal seats, were candidates won by such a small margin in the last election that they are at risk of being easily defeated. A list of marginal seats at stake in the 2015 elections shows 93 seats that were won by 10% or less, including 52 seats with a margin of 5% or less.

1792 candidates have registered to contest the 2015 election. The Hill Times provides a handy list of the major party candidates for each riding. You can download the final list of all confirmed candidates from Elections Canada in either an Excel file or as a pdf.

Incumbent MPs have something of an advantage in elections, since they have had the benefit of experience and the public exposure that comes with serving in office. As a result, interesting contests occur in ridings where the sitting MP has decided not to run again.

Milton Chan runs a unique site providing riding-by-riding predictions of the contests in each constituency for national and provincial elections  This site relies on people submitting their assessment of ridings that they have local knowledge of. Connect to the site and add your two cents worth! This site was uncannily accurate in the past, correctly predicting 91% of the seats in 2008 - although the success did drop to 76% for the 2011 election.

Since our electoral system is created around local elections, one would think that local candidates would play an important role in people's decision about whom to vote for. However, opinion polls have consistently found that Canadian voters overwhelmingly decide how to vote on the basis of party leaders or platforms. A Nanos poll conducted in March 2011 found that only 12% of Canadians felt that the local candidate was the most important factor in deciding how to vote; 48% said they were most influence by a party's policies, 20% by the party leader, and 10% simply said they traditionally vote for the party. This trend was evident in an Ekos poll released at the start of the 2008 campaign, in which less than 9% of respondents claimed that the local candidate is the main factor in their decision. An Ipsos poll conducted Sep 17-18 asked a somewhat different question but still found only 17% saying that local candidates were their most important consideration. You can read an interesting academic paper on the importance of individual candidates: "Does the Local Candidate Matter?" (pdf file) by André Blais, Elisabeth Gidengil, Agnieszka Dobrzynska, Richard Nadeau, Neil Nevitte.

Readjustment of Electoral Boundaries
 

Each decade independent Electoral Boundaries Commissions are set up to review the distribution of seats in the House of Commons to ensure that the number and size of each province's constituencies meets the legal requirements.  The Supreme Court of Canada has ruled, in the Electoral Boundaries Reference case, that Canadians should have a relatively equal voting power. As a result, the number of voters per constituency should not normally vary more than + or - 25% from the average. From time- to time, new ridings are added, and at others the seats are redistributed among the provinces.  The methods used to allocate seats among the provinces and to draw boundaries has changed considerably over the years. The previous readjustment of electoral boundaries was done in time to come into effect for the 1997 general elections.  Prior to 1985, adjustments to federal boundaries were achieved by amending the British North America Act, 1867; since 1985, however, the changes are incorporated into ordinary law. Section 51(1) of the Constitution Act, 1867 and Electoral Boundaries Adjustment Act governs the process currently used.

However, riding populations can shift dramatically within short periods of time. You can look up the differences in the populations of each riding, to see how they have changed between the 2001 and 2006 Census. Just in this 5 year period, the population changes range from -7.6% in BC's Skeena - Bulkley Valley to a whopping 52.5% in Ontario's Oak Ridges - Markham. StatsCan has a sortable table of population and dwelling statistics for all the federal ridings. You can also download an Excel file with all the population and dwelling data for Canada's electoral districts.

The 2011 general election was conducted using the same 308 ridings contested in the 2008, 2006 & 2004 elections; by contrast there were 301 constituencies in the 1997 and 2000 elections. The 2006 elections were conducted with the same electoral boundaries used in the 2004, with the exception of two constituencies in New Brunswick: Acadie–Bathurst and Miramichi. Note that a few ridings have new names since 2004, but their boundaries have remained intact.

Because the boundaries of electoral districts changed between the 2000 and 2004 elections it is necessary to transpose the results on a poll-by-poll basis before you can compare the results on a riding-by-riding basis. You can see how the 2000 elections results would have been under the new 308 seat distribution (Adobe pdf file). Elections Canada also shows what the results would have been on a riding by riding basis.