When I plug Forum's regional numbers into my model (which means I am using the exact same data that Forum is using, with the same regional distribution), I get 45 seats for the PCs, 41 for the Liberals, and 21 for the New Democrats. It is very difficult to fathom how Forum can get the NDP at just 13 seats with 22% support - exactly where they were in 2011 - with the PCs up just two points over that election and the Liberals down almost five. In fact, I'd have to have the NDP at around 18% support before I'd project them to have 13 seats.
To put that into context, if Forum's vote and seat numbers were exactly what happened in an election, it would rank as my model's 11th worst performance over 13 elections.I have seen some Twitter commentary to the effect that I did not discuss regional numbers but my experience using regional data tells me that it is not that robust. It cannot account for Forum's odd results or the extreme seat differences between the two polls.