The English media have to a large extent described the LibDem collapse in Scotland in terms of dissatisfaction with the CoLD coalition.
However, although this is bound to be part of the explanation, I don't think one should underestimate the part played by their own sheer incompetence in the Scottish Parliament.
As I blogged exactly four years ago, the LibDems behaved very strangely in refusing to even sit down with the SNP.
Back then, the obvious interpretation was that they only wanted to form a coalition with Labour, but now that they're in a coalition with the Tories in Westminster, insisting on a Labour coalition up here seems a bit odd.
I think many voters asked themselves who would govern efficiently and stand up to Westminster in a constructive manner, and almost nobody thought that the LibDems were the answer to that question.
They need to redefine themselves. Perhaps, as suggested by Liberal Vision, there is a gap "on the pro-independence centre-right" that they could fill. I'm sure that would work better than whatever it was they tried over the past four years.
Let's see what the new leader decides to do!