As this weekend's post-mortems of the Gorton & Denton by-election get under way its worth making the key point that I'm sure will be made anyway:
Its not so much that Labour voters have abandoned the Labour Party, but more the Labour Party has been abandoning its Left voters for years;
the lesson of Thursday is taking the Leftish for granted only works when there is no Left alternative.
If Thursday changed anything, it made that much, much clearer!