Nobody ever won a General Election without people who hadn't voted for them before changing to vote for them, including many people who had voted for other parties, obviously.

Former Tory MPs have crossed the floor and even become Labour Ministers. And of course Winston Churchill was a Liberal MP before he crossed over and became a Conservative.

Calling people who have backed the Greens or left parties "entryists" is a bit absurd.

Primary elections in the States are often conpletely open affairs - and when Harriet Harman announce this electoral system earlier this year she specifically said that anyone on the electoral roll would be entitled to sign up and vote for the party leader. Of course they moved the goalposts after that.