David Miliband has jumped on the bandwagon and declared that Labour should adopt the US style of primary. In doing so he is subtly altering the ground set by the Conservatives with their Totnes selection.
In Totnes, the selectorate was the entire electoral register. All well and good (if you can afford it). Future selections that follow this pattern won't get quite the same media attention, but if the parties (any of them) want to do the same thing then bully for them. It is, as others have noted, a great campaigning tool.
What Mr Miliband wants is something different. He wants to allow registered Labour supporters to play their part in selections. I have no doubt that the unions - currently a significant part of any Labour selection - will object to this. But my real problem is that, by limiting participation to registered Labour supporters, he is asking the taxpayer to foot the bill.