Why Labour did so well in 2014 Wythenshawe by-election

http://en.wikipedia.org/wiki/Wythenshawe_and_Sale_East_by-election,_2014

The Wythenshawe and Sale East by-election results were analysed in the following terms by an old BNP hand:

"Classic two party system vote swings.  When there is a Tory government Labour vote gradually climbs and vice versa.  In a Labour government the BNP will always do better too as Labour voters switch to the BNP quite easily as a protest.  You will see that in the Labour years that the European election results the drop in the Labour vote was almost exactly equal to the rise in the BNP vote.  UKIP take votes from the Tories."