The surge in national support for the NDP is quite remarkable (outside of the Prairies where they are down) but not historically novel. Before the Reform Party the NDP polled quite well during federal elections in BC. The BC story is therefore somewhat of a reversion to mean story. The same can be said about Ontario. The novelty is Quebec and the Maritimes matched with a resurgence of the NDP in Ontario and BC.
In this election it could well be that Quebec is where the two party system will come to its end . Montreal has gone, en masse, to the NDP and that is the single biggest story of this election. Montreal (42.6%) appears to view the NDP as the main place to park their federalist vote. That linked with the mopping-up of the soft nationalist, strongly progressive cohort of voters in Quebec would seem to indicate that the NDP could be very well headed to the status of official opposition / government in waiting.
Nobody predicted any of this and making sense of it will take some time.
Relentlessly Progressive Political Economy 
What do you mean unthinkable? It’s been thought about since the 1960’s when the NDP first came on the scene!
I did not write “unthinkable”, I wrote “unprecedented.”
Oh and the CCF had the same dream. So well before the sixties.
http://www.cbc.ca/news/politics/canadavotes2011/realitycheck/2011/04/polling-and-the-ndp-surge.html?ref=rss