As every first year Canadian politics class covers ad nauseam , the first past the post electoral system is great for large parties and terrible for small ones. Since you only win MPs by winning a plurality in each electoral district, parties that have a small but significant amount of support spread between many ridings may end up electing almost nobody while the parties that win the largest share of the vote end up with an even larger proportion of the seats and usually all the influence.
The sheer difficulty of electing someone from the Green Party as an MP makes running a bit of a quixotic gesture, with most candidates, staffers, and volunteers aware that their chances of winning are negligible and so the value of participating in the election may be about contributing to the discourse rather than a hope of victory.
With each Green MP so precious and unlikely, it must be especially galling to see Fredericton MP Jenica Atwin cross the floor from the Greens to the Liberals. At least according to the CBC, one reason she chose to make the change is Green Party infighting about the Israel-Palestine dispute. To me, this is suggestive of two things. First, how the agreed portions of a ‘green’ agenda don’t really add up to a complete set of policies, and so green supporters may have to deal with an unusual amount of in-party disagreement about non-environmental matters (and perhaps also on how to solve environmental problems). To me it’s also suggestive of the emphasis on symbolism and moral righteousness or superiority within the progressive left. It’s questionable whether Canada as a whole has any meaningful influence over the Israeli-Palestinian dispute, and it’s basically certain that a fringe party with just a few MPs doesn’t. That makes the dispute seem a bit like a high school student council voting on whether to praise or condemn a foreign government; it has considerable scope for generating conflict among those involved in the vote, but no real prospect of making a difference in the world at large.