Tonight's edition of Newsnight is going to include the first live televised hustings of the Labour leadership contest. This will be the biggest audience for any hustings so far and is going to have a very different dynamic.
All politicians respect Jeremy Paxman and all the candidates have already done one-on-one interviews with him on the show. But tonight's Newsnight is going to include a studio audience, not of committed party members who will cheer for their chosen candidate, but an audience of swing and former Labour voters. If one of them passionately challenges a candidate, we could get the equivalent of the Gillian Duffy/Sharon Storer/Joe the Plumber moment of this contest.
When Newsnight put together a focus group earlier in the contest, nine swing and former Labour voters unanimously picked David Miliband out as their choice, after being shown clips of their speeches from last year's party conference. Partly on the back of that focus group, David Miliband's supporters began to argue that he was the was the candidate who could win back the support of all sections of society and refresh Labour's offer to reach parts of the electorate that others couldn't reach.
That, however, was before Diane Abbott entered the race. Abbott probably has more TV experience than any of them because of her weekly This Week slot. And we shouldn't forget that David Miliband's campaign made a conscious decision to give her the nominations she needed to get on the ballot paper.
Time will tell whether that was a politically strategic masterstroke or New Labour's final blunder. At last week's New Statesman hustings, David and Diane clashed on Trident and Iraq in exchanges that can't have helped him win any votes in the party, though no doubt his arguments would have had greater resonance with the electorate. At every hustings so far, the audience has been packed with the politically engaged left, not the aspirational hard-working families of rural Kent, Bedfordshire or Buckinghamshire.
Ed Balls has had recent experience of a Newsnight hustings in the show on education before the last election. But there will be no Michael Gove on the panel tonight. At every hustings so far, Balls has been the strongest in terms of attacking the Lib-Con coalition, last night saying that Nick Clegg was a man who would stop at nothing to gain power, even supporting a regressive rise in VAT. The problem for Balls is that the very limited polling of party members available -- just 650 techno-literate LabourListers -- shows him falling to get a popular return for this formidable Tory and Lib Dem bashing.
Andrew Neil put the four ex-ministers to the test during the election when the Daily Politics ran six hustings on foreign policy, health, education and climate change, as well as crime and immigration. David Miliband more than held his own against the formidable William Hague and Ed Miliband absolutely wiped the floor with Greg Clark (remember him?) while managing to distinguish himself from Simon Hughes and the Green spokesman Darren Johnson.
Last night's hustings at the Institute of Education was the most jovial, but TV is very different. The candidates are getting more comfortable in each other's presence. There is a comradely camaraderie developing between the five of them as they put the hours in and travel the country. They are all having a shared experience. Yet the atmosphere in the Newsnight green room tonight will be very different.
Any slip-ups, gaffes or controversial talking points will get played out at branch and ward meetings across the country and in newspaper columns for the rest of this week. Tonight could be the first impression that many party and union members get of all five contenders standing side by side, giving them the chance to make a snapshot comparison.
Whatever the Labour Party equivalent of a water cooler moment is, it is likely to happen tonight. "Did you see Newsnight last night?" will be the question du jour for Labour tomorrow.
Richard Darlington is head of the Open Left project at Demos.