Could 'Corbynmania' swing the London Labour mayoral race?
The number of people registered to vote for Labour in London rose from about 40,000 in May to 120,000 this month.
Some 6,000 of those have been struck off the voting list either because they were counted twice or they were not "real" supporters, according to a Labour source.
But these new voters take the London race into uncharted territory because very little is known about how they will vote, and that's getting the candidates in this six-horse Labour mayoral race salivating.
Dame Tessa Jowell, viewed as the clear favourite when she launched her campaign in May, is still leading the polls.
Yes we Khan?
But if you presume, as Tooting MP Sadiq Khan's team does, that many of the new voters have signed up to select Jeremy Corbyn because of his left-wing stance, perceived wisdom might suggest they would not vote for Dame Tessa as she is viewed as the Blairite candidate.
Labour's vote held up in this year's general election. But the mayoralty has long proved elusive to the party, and given that Londoners have twice elected a Conservative mayor over Corbyn enthusiast Ken Livingstone, some may question whether having a left-wing candidate would necessarily be an asset in next year's election.
But some of the mayoral hopefuls clearly do feel they can benefit from a resurgence on the left.
That line is certainly being peddled by union-backed Mr Khan, who says he's attracting the Islington North MP's supporters - although he has also openly said he probably would not work under Mr Corbyn as Labour leader.
Mr Khan's spokesman told me the new voters included "older people who had left Labour because of Iraq, and young idealists in the public sector excited by Jeremy Corbyn" who are more likely to vote for a left-wing candidate.
The trouble with the argument that Corbyn voters could shape the battle for City Hall is that there isn't one clear left-wing candidate for them to champion.
No Abbott surge
Hackney MP Diane Abbott says she is "the closest to [Mr Corbyn] politically". But the polls do not reflect an Abbott surge and Mr Corbyn hasn't backed her or any other London candidate.
Another left-winger, Christian Wolmar, says he too will mop up more second preference votes because of the "Corbyn effect".
But Dame Tessa's team insists there is "no evidence" that she isn't attracting these new voters and says she "isn't seen as a factional Labour politician".
The centrists meanwhile - David Lammy and Gareth Thomas - are also claiming to be winning over the new voters who they say haven't put much thought into the London race.
Whether these new voters will favour the left, or vote on policy or personality remains to be seen. What is clear is that the fresh meat weighing in to vote in the Labour's leadership contest seems to have spiced up the Labour mayoral race as well.