Prometheus: Let's say the Liberals and NDP together get 48% of the vote, the Tories get 49%, and Christian Heritage gets the minimum 3%. If the Tories wanted to implement something, it could well be the Christian Heritage party that puts it over the top. That's just one of many possible and in fact quite probable scenarios, when you consider that 48% is exactly the percentage of the vote that the Liberals got last time. Just one looney party to put them over the top! You can imagine what such a party would ask for in return.
That's been the situation for years in Israel, for example, where the tiny settler and religious parties are needed to put the major parties over the top into majority territory.