The Staggers 12 August 2015 Who will win the Labour London mayoral contest? The influx of left-wing members has led some to doubt Tessa Jowell's chances. Labour's London mayoral candidates attend a hustings on 30 July, 2015. Photograph: Getty Images. Sign UpGet the New Statesman's Morning Call email. Sign-up What does Jeremy Corbyn's remarkable lead in the Labour leadership contest mean for the party's London mayoral selection? That is the question MPs are beginning to ask as their minds turn to the other election taking place. The opposition has a far better chance of winning the capital next year than it does of winning the country in 2020. London is a Labour city (the party won 45 of its 73 seats and 44 per cent of the vote at the general election) and the likely Conservative candidate, Zac Goldsmith, cannot match Boris Johnson's popularity. Unlike the contests for leader and deputy leader, which Corbyn and Tom Watson will almost certainly win, the mayoral race remains open. It is Tessa Jowell, the former cabinet minister, who has long been regarded as the frontrunner. Jowell, best-known for her Olympics role, owes this status to YouGov polls of London Labour voters giving her a commanding lead over her rivals: Sadiq Khan, David Lammy, Diane Abbott, Christian Wolmar and Gareth Thomas. But these surveys are not necessarily a reliable guide to who will win the nomination. Just as polls show Andy Burnham ahead of Corbyn among Labour voters but behind among the party selectorate, so Jowell could lead among the former but trail among the latter. Party sources expect around 105,000 to be eligible to vote in the contest, of which 40,000 are existing members, 20,000 are new members, 25,000 are affiliated members (belonging to trade unions or socialist societies) and 20,000 are supporters. With private polling showing Corbyn on course to win around 70 per cent of first preferences in London (compared to 53 per cent nationally in the most recent YouGov poll), some in the party are now doubtful that Jowell, an unashamed Blairite, will triumph. The left-leaning Sadiq Khan, who is backed by Unite (and who nominated Corbyn), and Diane Abbott are likely to benefit. Khan's opposition to the Iraq war and his recent vote against the welfare reform bill are said to be aiding his campaign. But a Jowell source said that their phonebanking did not suggest any significant change in the state of the race and that Jowell's "positive vision" was attracting support from all wings of the party. As well as leading in YouGov polls, Jowell led Khan by 39-34 in a survey of Unison members, and has led in polls of LabourList readers. The recent influx of left-wing members could reduce her lead without eradicating it. In Jowell's favour is that she is a probable winner in a contest taking place next May. The Corbyn surge partly stems from the distance of the next general election and the failure of any of the candidates to look like a prime minister-in-waiting. Activists feel empowered to enjoy a "free hit" (as Chuka Umunna put it to me). But until a poll of the Labour selectorate is published, the London contest will remain harder to call than any other. › In this week's magazine | The Battle for Calais George Eaton is senior online editor of the New Statesman. Subscribe For daily analysis & more political coverage from Westminster and beyond subscribe for just £1 per month!