Despite a long history of Euroscepticism, the Labour Leader surprised some in the autumn when he agreed to support a Remain vote as a concession to his Shadow Cabinet. It typified his judgement that the only issue on which he was willing to compromise was the one on which he was correct (albeit correct for the wrong reasons).

But it increasingly looks like his support could prove to be a double-edged sword for the pro-EU campaign – Corbyn could still end up helping to secure a Leave vote in the referendum.

Consider the following factors:

  • Organisationally, he has neutralised Labour. We are told that the Labour Party won’t be putting very much of its own money or resources into the Remain campaign, beyond a small amount of seed money for Alan Johnson’s effort. The Party could spend some £4 million if it wished – under a more enthusiastically pro-EU leader, with better relationships with donors, it might have done so.
  • The unions are now free. Events in Greece, and the TTIP proposal, have led to a limited rebirth of left-wing euroscepticism (a movement that had been dormant for some time). Where a stronger leader might have restrained the unions from flirting with that shift, Corbyn has set them free politically – and Unison, the second-biggest union, is now considering whether to recommend its members vote Leave.
  • He wants to drag the Remain campaign into actively arguing for free movement. While the pro-EU campaign is trying to cling to the threadbare renegotiation as evidence that Cameron’s reforms will address public concern about immigration, Corbyn has other plans. The Observer reports that he intends to condemn the Prime Minister’s deal as discriminatory against Eastern Europeans – all from a position of supporting Remain. This is precisely what the pro-EU campaign has tried to avoid, as it will highlight one of their weakest issues to Labour voters.
  • His poor polling performance makes it safer for Tories to disagree with the Prime Minister. I reported on Thursday that the Remain pitch to grassroots Conservatives is focused on the idea that this vote is about personal loyalty to Cameron. Oliver Letwin is also reported to be arguing that a Leave vote would be harmful to the Prime Minister. But that fear seems rather unconvincing – partially because this is about the future of our country, rather than the short-term prospects of our Party leader, but also because it’s hard to see Labour as a serious threat or a serious alternative. The Independent on Sunday reports that despite the unpopularity of Cameron’s renegotiation package, the Conservative poll lead has grown to 14 points. It is clearly possible to ‘vote with your heart’, in Cameron’s words, by backing Leave without in any way harming the Conservative Party.

Perhaps the Remain campaign could come to wish that Corbyn hadn’t agreed to support them after all.