The Professor Will See You Now: Ranking MPs' politics

One of my favourite articles on voting in the House of Commons saw an attempt to apply a widely used technique in US legislative studies – which failed badly. The Optimal Classification procedure generates plausible lists of Members of Congress from left to right, based on their voting.

But when applied in the UK, using data from the first Tony Blair parliament, it generated a ranking of MPs that had Giles Radice as the most left-wing member of the PLP and Bernie Grant as the most right-wing. 

That it wasn’t working was clear; more interesting was why. The problem wasn’t that the authors had done anything wrong but that votes in the Commons often see unholy alliances; when the Campaign Group were in the same lobby as the Conservatives voting against the government, they were doing so for very different reasons. 

To this we can add a further issue with voting data: relatively high levels of party cohesion mean that while it helps differentiate MPs at the rebellious end of a party, it’s of less use when it comes to sorting the more cohesive. Free votes don’t help either; by their very nature they are atypical and tell you little about the more central cleavages in a parliamentary party.

Given all this, researchers have looked elsewhere for ways of divining the ideological positions of parliamentarians: EDMs, speeches, surveys and so on. One new technique, written up in a recent article in the British Journal of Political Science, attempts to use MPs’ presence on social media. Drawing on data from Twitter/X, it works on the basis that ordinary users (if you are reading this, by definition that doesn’t include you) will follow people they perceive to be close to them politically. Analysing the groupings of around half a million X users, the researcher constructed a scale of MPs.

The good news: that scale mapped pretty closely on to actual political events. The Conservative rankings, for example, proved good at predicting MPs’ nominations in the first leadership contest in 2022. The less good news: not only is the data already out of date, given the election, but it would be difficult to use X for a similar study now and no alternative ecosystem has yet emerged to replace it. But at least the method seems to work. 

An intriguing alternative is being developed by Chris Hanretty and Vasil Lazarov, surveying councillors about their local MPs. (Councillors might not know about every MP, but they will have a good understanding of their local ones.) Do that across enough councillors and you can build up a map of the entire parliament. The first exercise was done in late 2023; it was then repeated after the election.

Of the current parliament, it has Nadia Whittome, Bell Ribeiro-Addy and Diane Abbott as the three most left-wing MPs, and Suella Braverman, Iain Duncan Smith and Rupert Lowe as the most right.

Hanretty is to British political science what Neil Peart was to drumming (whereas I am much more Pete Best), so he is too smart to take the data at face value. Some obvious biases: because councillors rank according to the local patch, this can skew things (to quote one of their own examples Rebecca Harris looks suspiciously left-wing in the survey because she’s compared to lots of right-wing Conservative MPs in Essex); respondents also seem to be making assumptions about ethnic minority MPs being more left-wing than they actually are. But as with the Giles Radice-Bernie Grant switcheroo, many of these issues are revealing in their own way.

The aim is not to generate a perfect ranking, because that doesn’t exist. The question is whether these are good enough. It’s explained at mpsleftright.co.uk, and if you are an MP and you haven’t looked yourself up yet, I’m very disappointed in you. 

Further reading: A Spirling and I McLean, UK OC OK? Interpreting Optimal Classification Scores for the UK House of Commons, Political Analysis, 2007; Estimating Ideal Points of British MPs Through Their Social Media Followship, British Journal of Political Science, 2024

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