The Better Off Out pledge requires that sitting MPs who publicly endorse the fact that Britain would be better outside of the EU, require a free run from UKIP in their constituencies.
I have changed my stance on this, from being a firm supporter of the BOO pledge to more of a sceptic. After all, where were all of these MPs - largely Tory - in the media when Cameron turned tail on his referendum pledge? Only Bill Cash really spoke out, and he isn't even one of the BOO set. The argument is that UKIP shoudn't cost these people their seats so they can make the anti-EU argument in the Commons, but if they are going to be partisan to the point of not being critical, then it seems a bit of an empty pledge.
There is also the question as to whether we want UKIP to be seen as a one issue Party. An MP like Bob Spink may be anti-EU, but disagree with UKIP on a whole range of other policies. Is UKIP right as a Party to simply care about that MPs stance on that one issue if they are happy to vote for 42 days? I'm not convinced.