Sean, I agree you laid it very clearly. I would just like add that each party probably has a base of seats that are very solid. Whether it be strong voting culture, on the ground organization or well liked candidates there will be some ridings that hold their vote when the general party vote collapses. You can save the furniture.
Absolutely -- I think though that for some parties this concentration may included more than needed to hold the seat -- and that means extra votes that do not deliver more seats. A party that is low in a pile of places and then in a few places up to 60-70% has lots of wasted vote in places where it is more than they need or not enough to benefit. This is inefficient. and also as you say there are voters that are more solid than others -- and these are not distributed evenly so you could have a concentration saving a few seats when overall support drops. This is the thing seat prediction sites miss and why I think the Liberals may hold 5-6 seats when the raw vote only points to 0-2, for example.