Biggest vote loses in the four by-elections

Change in vote from 2011 General Election

1. -14,799 CPC     Provencher
2. -10,181 CPC     Brandon-Souris
3.  -9,580 CPC     Toronto Centre
4.  -6,808 NDP     Brandon-Souris
5.  -6,783 Liberal Bourassa
6.  -6,554 NDP     Bourassa
7.  -5,751 Liberal Toronto Centre
8.  -5,214 NDP     Provencher
9.  -4,175 NDP     Toronto Centre
10.  -3,718 Bloc    Bourassa
11.  -2,502 CPC     Bourassa
12.  -1,769 Green   Toronto Centre

What I find interesting is that the top three are all Conservatrives.  Also interesting is that in all four by-elections the winning party, which had held the seat in 2011, lost more vote than their main opposition.

The Liberals were the only ones to gain votes anywhere, they increased their vote by 9,932 in Brandon-Souris and 4,061 in Provencher