"'Selective' Tories try to lower by-election expectations"

That was Jane Taber's morning buzz, reporting that the government was trying to lower expectations in the upcoming byelections based on a memo Tory strategists circulated to MPs: "The Government in power very rarely wins by-elections, especially in ridings they didn’t win in the previous general election. Official opposition parties win by-elections, and two of these ridings have been held by opposition parties for decades."

That was not an accurate statement by Tory strategists. This government in particular has performed very well in byelections. There have been 13 federal byelections in Canada since Stephen Harper first became Prime Minister. 62% of those were won by the party defending the seat. Of the 5 byelections that went to a new party, 4 flipped to the Conservatives. So yes, the incumbent party is most likely to win, but when they switch they are most likely to turn Tory blue. The Harper government has also successfully defended all the Tory ridings that came up for byelection. 

I did not continue further to pre 2006 byelections because I have to get ready for work. That data is available at the Elections Canada website if anyone wants to look up how Martin and Chretien performed in byelections while in government.