Take Labour leadership polls with a pinch of salt – we still have no real way of knowing who’ll win

Party leadership contests are notoriously difficult for political correspondents to get a handle on.

In the olden days, when Tory leaders were picked by MPs and Labour had a complex college system in which trade unions wielded bloc votes, it was easy to take soundings inside the Westminster bubble and form a shrewd judgement on who was in line for the top job.

But with democratisation of the process in all the major parties, decision-making power now lies in the hands of the membership – and also in Labour’s case with “registered supporters” and members of affiliated unions and groups like the Fabians or the Jewish Labour Movement.

Although they number hundreds of thousands of people in total, these are groups which are very difficult for pollsters to survey accurately without access to membership lists. A conventional poll of a few thousand voters selected at random is unlikely to pick up enough party members to offer any meaningful insight into their likely preferences.

And the one-person-one-vote system means it is difficult to predict how members will act. A union boss may throw his or her weight behind a particular candidate, but there is no guarantee that rank-and-file members will follow. The preferences of MPs are often roundly rejected by their constituency parties, as seen in 2015 when Jeremy Corbyn struggled to get enough parliamentary support to get onto Labour’s ballot paper, but won a landslide in the country.

Anyone trying to forecast how this electorate will vote needs to remember that by definition party members are not typical of a society where few people join political parties. Their political commitment is stronger, their loyalties more deeply rooted and their opinions are likely to be more “extreme” – not only than society at large, but also than their own party’s MPs and voters. For many, establishing the dominance of a particular strand of thinking within their party may be more important than finding a leader who can win an election.

While Westminster muses over whether Labour should pick a woman, a northerner, a Leaver or a Remainer, a Corbynite or a centrist, to have the best chance of winning back its lost heartland seats, members might be motivated by entirely different considerations.

For all these reasons, the YouGov poll giving Keir Starmer a commanding lead over potential rivals to succeed Corbyn is fascinating, but should also be taken with a pinch of salt.

First of all, it does not include registered supporters or members of affiliated groups, both of which broke heavily for Corbyn in 2015 and 2016 and might be expected again to back a more leftist contender.

Secondly, the cut-off date for new members to have a leadership vote has not yet been fixed, and activists on all wings of the party are busy recruiting to boost their favourites’ chances.

And third, we don’t yet know what the line-up of contenders will be. The final choice may depend on the balance of candidates and on who comes to be seen as the champion of the left or the centre. In 2015, Corbyn’s insurgent campaign was enormously boosted by the perception that he was the sole socialist standing against a middle-of-the-road array of three identikit rivals. Members also responded well to a fresh face who was virtually unknown to many voters before the campaign – something which may favour backbench hopefuls like Lisa Nandy or Clive Lewis this time.

So the YouGov poll is a boost for Starmer and a challenge to those who claim Labour has irrevocably fallen into the iron grip of the left. But it’s far from the end of the story.

Yours,

Andrew Woodcock

Political editor