Trudeau made a lot of promises last election the key one being on electoral reform. Many voters were drawn to the Liberal tent because of this promise and  the breaking of it will send those people back out. I can't see the Tories embracing Proportional Representation so the field is open for the NDP who, along with the Greens, have advocated for it all along. Add to this a charismatic leader like Singh and there could be interesting times ahead.