I left this comment on Scott Tribe’s blog just now with respect to the Liberal/Green arrangement in Central Nova…

This situation illustrates how problematic our first-past-the-post system really is in a multi-party state. We tried to make it work for about 60 seats as a 3-party system (the result being that we see and increasing number of MPs winning with 30-35%, and a parliament that often bears no relation to the first-preferences of Canadians). The situation became even more odd after 1993 with the right vote split across 3 parties, due to the birth of Reform and the Bloc, which allowed the Liberals to rule unopposed for over a decade (with 38% 40% of votes resulting in 60%+ of seats). It is also resulted in one of the founding parties, the Tories, being killed off — subsumed into the new Conservative Party. By limiting electoral choice on the right, the situation has improved somewhat in terms of the vote/seat mismatch (but with the obvious problem that we have less choice now). But suddenly, with the rise of the Greens, we are back to trying to make an electoral system that was designed for a 2-party system work with a 5-party system. That leads to the kinds of arrangement made between the Greens and Liberals. If the progressive vote is now being split across 3 parties (possibly 4 in Quebec), if non-compete arrangements aren’t made, then the other natural result will be a merger of progressive parties (the same as happened on the right), again limiting choice. Some have even speculated that the rise of the ADQ in Quebec (and subsequent fall of the PQ) suggests that some of the old rural Quebec conservative vote may well re-align with the new Conservatives. With consolidation happening on both the left and right, you see where this is headed: the winner-takes-all nature of our electoral system tends back towards 2-party rule, which is of course, what it is designed to do (at best, it will lead back to 3-party rule). What this agreement between the Liberals and Greens suggests is that it is long time to add an element of proportionality to our electoral system so that Canadians can have real voter choice where their votes really count — a system where we keep our local MPs but add regional MPs elected on a proportional basis. Only then will voters have real choice and get the parliament they really asked for.