Maurice Picarda
Actually, might as well flounce.
I thought the 'registered supporter' had a nominal charge attached - a quid or three quid, something like that. Wolmar (who's running a grass roots campaign for the Labour nomination) was pushing it recently. It's an attempt to get people on board cheaply, but more importantly harvest contact details for future spam.
Tories were trying a similar thing in some seats, having open primaries, because the bonus of doing this is it makes people aware of the candidate, a bit of mass publicity in advance of the election. I'd vote for the most charmless or freakish looking candidate just to hamper their chances.
I think it was decided that there would be a £3 fee for voting in the mayoral election; perhaps the cost for voting in the leadership one is yet to be established.