Anathema to democracy. Hunh.
I was an NDPer for my whole life until I switched to the Liberals. I made the complete move over to the Liberals just this year, but the transition was many years in the making (and I was active in the last provincial Liberal campaign). During my transition period, and even before, I was a strategic voter.
What did this mean? In my case, it meant I supported a party I didn't particularly want to get into power. I supported the NDP because of the alternative voice the NDP brings to debates. (For details, see Why I Left the NDP.) I still support the NDP in that regard, even though I am currently a committed Liberal member. The NDP has a lot to offer the country and we would be greatly diminished without its presence in parliament. In particular, the NDP has had a positive influence on the Liberal government and has pushed them to places they might not have gone otherwise - does anyone remember Jack Layton's deal with Paul Martin's minority government in 2005? I'm going on about this because the Liberals and NDP are natural allies, and there is always going to be a large, responsible area of cross-over among supporters of each.
So then why, as an active NDPer, did I consider voting Liberal in many elections? Of course the main reason was that I weighed my support for the NDP against my dislike of whoever was currently the Tory leadership. But strategic voted started for me with the 1979 election, when I voted for my preference (NDP) and then was not happy when Trudeau was defeated. So in the 1980 election, despite preferring the NDP leadership and my local NDP candidate, I voted Liberal. I have never regretted it.
But in some elections I was genuinely torn. Frequently the NDP candidate in my riding (and I have lived all over Ontario) was not of the highest calibre. In that case I generally voted NDP to help the party attract better candidates in future. But if I liked the Liberal candidate and it was a close race between the Liberal and Conservative, it could be difficult to support an NDP candidate I didn't respect, even though I wanted the NDP to do well nationally.
During my transition to a Liberal I also practised strategic voting. If my Liberal candidate looked dead-set to win, I'd consider voting for an NDP candidate, even if I wasn't thrilled with the person, just to make it possible for the NDP to attract better candidates in future.
I know that strategic voting is controversial because my friends in the NDP used to rail at me about it. But it seems perfectly democratic to me. No matter what system of voting we use, in the upcoming federal election I would find a way to vote that was most harmful to the chances of the Harper government. If the Tories move back to their (pre-hostile takeover) roots and elect a leader (and MPs) who are less stridently right-wing, then Canadians might not feel the need to be so strategic.