The leftist Brexit urge is irrational

Picking up a point I tweeted about a few days ago, and, I think, also pointed out independently by Chris Giles....

It's a curious thing that the right in the UK may want to leave the EU if David Cameron does not succeed in watering down labour market and social protections that bind the UK enough.  Yet, if he does, this will prompt the UK left to want to leave.

And thinking about it the left's desire to leave seems irrational.  If rights get watered down, there's still the option of topping them up locally.  And the watered down rights that remain imposed centrally by the EU act like a guaranteed minimum.  If the left were to vote to leave, in a strop, this would expose their workplace constituents to the rise and fall in their own fortunes.  In years of electoral wilderness (say, for example, hypothetically, the next 25 years), the right could chip away at these rights so that they were below the minimum that remaining members of the EU enjoyed.

The right's desire to leave is more internally coherent - even if I don't support that either.  From their point of view, there is no recourse to local watering down if the centrally imposed minimum level of protection is not sufficiently low.

Perhaps this will all be academic.  Peter Doyle pointed out to me that if Corbyn makes the Labour Party unelectable, this will lessen the need for Osborne and Cameron to worry about the right of his own Party, and make them bolder in campaigning for us to stay in an EU with no more than cosmetic reform.  For they can swap the deserting Tory UKIP voters for those on the right of the spectrum who would usually vote Labour.  Electorally, the latter are likely to be more decisive, since that switch would trigger a rush of marginals to go blue.