The options for Jeremy Corbyn on the EU referendum range from a weak In to a strong Out – given his history and outlook.  The issue is very live: Chuka Umanna seized on the topic yesterday to justify his resignation from the Shadow Cabinet, saying that “he had not received unambiguous assurances a Corbyn leadership would support Britain’s continued membership of the European Union in the coming referendum”.

What decision would best help the Out campaign?

One view is that if Corbyn backs Out, his decision will galvanise the new, young, urban-based, left-wing constituency that he is bringing into the Labour Party, and also raise the turnout among the party’s working-class base for Out.

Another is that nothing is more likely to frighten the mass of undecided people off Out more than Corbyn and Nigel Farage campaigning together for Out.  They will have the same effect on these voters as the combination of Tony Benn and Enoch Powell had in 1975.

My view is the latter, but what matters most is what Labour does not with its view but its resources.

It is now hard to see how the party’s cash and manpower can be poured decisively into either In or Out, given Labour’s own divisions on the EU question.  Until Corbyn was elected on Saturday, Labour seemed to be decisively for In – at least in terms of where its party members are.  But many of the new members and registered supporters are likely to lean to Out.  So, surely, is John McDonnell, Labour’s new Shadow Chancellor and Chair of the Socialist Campaign Group.

A weak In and resources neutrality (i.e: no party money or organisation for the campaign) would leave In very short of boots on the ground – which will matter come referendum day, just as it did last May.  This will be especially so if the Conservatives take a similar stance, a matter to which this site will return very soon.  If Labour’s machinery stays neutral there will certainly be less incentive for David Cameron and George Osborne to mobilise the Tory machinery for In – though they will want to do so in any event. There is also the question of what the unions do, and their interaction with Labour.

Some sources believe that Corbyn will call a special conference to decide.  If he does, it’s hard to be sure what such a forum will decide, given the volatility of events.  It is not impossible to imagine it turning Labour policy round.  And if Labour has one, there could be pressure on Cameron to hold one, too.  “How many times have you wanted to throw a bomb into the national assembly,” asked Poujarde. “Elect me, and I will be that bomb.” Corbyn has thrown a bomb into the EU Referendum calculations.

8.30am Update: Hilary Benn says that Labour will argue to stay in the EU “under all circumstances”. Hmm.