From the Toronto Star;

Since we have a multi-party system in Canada, this means that if no one large party gets a majority of seats, then a small number of seats can give a small party the power to make alliances and coalitions with others. It tends to be parties like the Greens and the NDP, which are far left parties. I think of them as the “conscience of the king”, and they tend to keep the “big two” (Conservatives and Liberals) in check, particularly if they are in a coalition position.