our immigration policy is far from perfect and could do with some reform but the amount of ex-labour voters willing to abandon their principles to vote for a Thatcherite simply because they don't like immigration is rather shocking.
It can be fully explained by the prolonged recession and sluggish economy. Basically, people have less money in their pockets, and look for something to blame for it.
Foreigners are the go to scapegoat throughout history for this. It is absolutely no coincidence that the rise of UKIP has came off the back of a recession.
But they are, ultimately, a protest vote, and will never be anything more. The problem that Labour supporters jumping ship don't realise is that they are effectively voting Tory by voting UKIP. They'll get a coalition Tory/UKIP government, which would be an absolute nightmare.
And if Milliband had any political talent whatsoever (which he doesn't), he'd be pointing this out over and over again.