The Labour Party’s current crisis is often characterised as an ideological dispute between the Parliamentary Labour Party and a membership that is significantly more left-wing. But, as Javier Sajuria demonstrates, it is hard to stand this up. The ideological distance between Labour members and MPs is in fact smaller than that between Conservative members and MPs. To explain why many are now suggesting that Labour is on the verge of splitting it is necessary to look at party rules as well as ideology.

The situation within the Labour Party has been described by many as a dispute between the Parliamentary Labour Party (PLP) and the membership. The en masse resignations from the shadow cabinet, followed by a vote of no confidence from 81 per cent of MPs, shows that Jeremy Corbyn has lost the trust of his peers (or perhaps he never really managed to obtain it in the first place). Labour activists, particularly those grouped around the Corbyn-supporting Momentum, accuse the PLP of betraying the party and lining up with the right-wing. On the other hand, MPs respond by pointing out that voters, and not members, elected them and that they have a mandate to protect the party from oblivion.

Regardless of how relevant it might seem under the current situation, the ideological distance between members and party elites is not a new interest for political scientists. John May’s curvilinear disparity law explains that more active members are usually more ideologically extreme than MPs and voters. As Meg Russell states in her book Building New Labour, there is a limit to how much a leader (or in this case party elites) can steer a party’s position to the left or right. Therefore, we could expect that a widening gap between members and the MPs may result in a difficult situation for the party, or even an eventual split. With that in mind, I set out to investigate – in a very preliminary way – if this ideological gap can explain Labour’s crisis, and if not, what are the alternative theories.

To measure the ideological position of the different groups, survey instruments usually carry a question asking respondents on where they see themselves in a left to right scale. These measures take values from 0 for left to 10 for right. In order to estimate the average position of party voters, I use the British Election Study post-election face-to-face survey. For the ideological position of the MPs I use the data from Parliamentary Candidates UK’s Representative Audit of Britain project, which surveyed candidates from the last general election. The estimates for party members and supporters were obtained from the Party Members Project (PMP).

In order to assess how unusual the ideological distance between the different groups of the Labour Party is, we can compare it to what happens on the other side of the chamber. May’s law is not circumscribed to a particular ideological position, so it should apply to parties of the left and the right. The figure below shows the ideological position on the left-right scale for every group in the Labour and Conservative parties. As expected, members and activists appear as the most extreme in both parties, whereas voters tend to position themselves closer to the centre. What is striking is that the absolute distance between members and MPs seems higher in the Conservative party (0.9 points) than in the Labour Party (0.6). Not surprisingly, Tory MPs appear to be closer to their voters than Labour MPs.

We can conclude two things from this graph. The first is that May’s law seems to apply to the current situation in both major parties in the UK. The second is that reducing the current struggle in the Labour Party to an ideological distance between the members and the PLP does not stand up in the light of evidence. If anything, the distance between members and MPs should produce more problems for the Conservatives than Labour. The Tories are indeed in the middle of a difficult process for electing their new leader, but few have seriously raised the possibility of a split.

Obviously, a left to right scale might not capture other dimensions of the ideological divide. The Guardian columnist Owen Jones has argued that the big red line among Labour Party members for electing a new leader is the candidates’ position on the war in Iraq – a prominent issue with only a few days until the release of the Chilcot report – rather than who is more left-wing. However, that argument implies that most politics within Labour can be explained by a single issue, which seems unlikely.

If ideology is not enough to explain the current crisis, then what is? I offer three complementary explanations:

In January, Meg Russell pointed out how Labour MPs have failed to understand their new role in the leader selection process. Following the rule changes introduced under Ed Miliband, MPs no longer have any more voting power than individual members, registered supporters and affiliated supporters. Rather, their role is similar to the one that Conservative MPs have in their leadership contents: gatekeepers. MPs are responsible for putting forward candidates that will not jeopardise the party, both electorally and organisationally. By letting Corbyn – who represents the most left-wing position amongst MPs – run for leader, they failed in their job to act as gatekeepers, and behaved as facilitators instead. The rules for selecting the leader allow for ideological polarisation by simply stating a threshold of supporting MPs (and MEPs) rather than a fixed number of candidates. Conservative Party rules require that MPs go through successive ballots until they submit only two candidates to the membership. Conversely, the Labour Party only required 35 signatures from MPs or MEPs to run for leader when there is a vacancy. This means that, theoretically, the last election could have had up to six different candidates (it had four). Instead of forcing an election between candidates who reach to all sections of the party (voters, supporters, members, and elites), the rules allowed for more polarisation which, as we see above, favoured the position of members over the rest. Finally, under the current rules, the leader of the Labour Party is not accountable to the PLP. This might seem obvious given that those voting for the leader are the members and supporters, not the MPs. However, the current situation shows how important it is that the leader is able to bring together all groups within the party. As we have seen earlier this week, not even a vote of no-confidence with over 80 per cent support can force Corbyn to resign, nor stop him from putting his name forward in the event of a challenge of his leadership. Under the current situation, is difficult to see how the Labour Party can provide a strong opposition to the government, if any at all.

The main take home point from this exercise is that the Labour crisis is not (only) ideological. Preference heterogeneity within parties is a well-documented phenomenon and the internal mechanisms should be able to cope with it. This is exactly what has been failing in the case of Labour. MPs were not able to understand their role as gatekeepers and guardians of party unity, but also the rules do not give them enough power to fix the problem. It seems that in this case, the leader of the party is willing to test how much he can steer the party to the left before breaking it.

Thanks to Professor Paul Webb for sharing the descriptive data from the Party Members Project.

About the author

Dr Javier Sajuria is a Research Associate at the University of Strathclyde and the Constitution Unit.