The fight is on for the Gorton and Denton by-election on February 26. It is a three-way contest between Labour, Reform and the Greens. According to Electoral Calculus, a site which runs regular MRP (multi-level regression post-stratification) surveys, Reform will win with 32% of the vote, the Greens will come second on 23.3% and Labour third with 22.6%.
There is however a problem with MRP polls. They produce results that are far more variable than can be accounted for by standard sources of errors in surveys. For example, a different MRP conducted by Electoral Calculus in December last year gave Reform 335 seats, the Greens 52 and Labour 41 in a hypothetical general election. In contrast, an MRP conducted by More in Common at about the same time gave Reform 381 seats, the Greens nine and Labour 85. Both results are therefore highly questionable.
An alternative approach to forecasting involves conducting small sample surveys in constituencies holding by-elections. The trouble is that these are not very accurate – as the recent Caerphilly by-election for the Welsh Senedd proved. Based on polling, many believed Reform was a contender to win but it ended up some way behind Plaid Cymru.
The relationship between the Labour vote in general elections and subsequent by-elections, 2010 to 2026:
A third approach is to use historical data on the relationship between by-elections and general elections to predict results. If we examine a large number of by-elections, then a strong relationship between the two becomes clear.
When you compare the Labour vote share in the 58 by-elections held between 2010 and 2025 and the Labour vote in the previous general election in these constituencies, a good result for the party in a general election is likely to produce a fairly good result in a subsequent by-election.
In the 2024 general election, Labour obtained just under 51% of the vote in Gorton and Denton. We can use this to predict what will happen in the by-election.
To improve the accuracy of the forecast, we first need to account for unusual by-elections over the years which could distort results. For example, in the Batley and Spen by-election in October 2016, Labour took 86% of the vote. This was because none of the other mainstream parties contested the seat in recognition of Jo Cox, the MP whose murder by a rightwing extremist triggered the by-election.
Equally, George Galloway’s Respect party won a by-election in Rochdale in February 2024, just before the general election. This was largely the result of Muslim voters switching their support from Labour because of the party’s refusal to significantly sanction Israel, given what the United Nations described as the genocide in Gaza.
A third factor is that all these by-elections happened under a Conservative government except for the Reform win in the Runcorn and Helsby in May 2025. A change of government affects all voters, so this needs to be accounted for in the forecast.
Like all predictions, this one is subject to errors and the modelling is done using a multiple regression analysis. It predicts that Labour will win approximately 37% of the vote.
Reform and Green voting
Unfortunately, we cannot use the same approach to forecast the Reform and Green vote shares because the historical data on the performance of these parties in by-elections and general elections is not available. They didn’t fight many of these constituencies in either type of election.
An alternative approach is to focus on the Runcorn and Helsby by-election, which Reform won by a whisker from Labour with just under 39% of the vote. Between the general election and the by-election, the Labour vote share fell by 14%, the Reform vote increased by 20% and the Green vote increased by just under 1%. If Reform repeats this in Gorton and Denton it has a good chance of winning.
However, there are good reasons for thinking that Reform will not be able to do this, because of the socio-economic characteristics of the constituencies. We can compare them with the help of data from the 2021 census to find out what characteristics favour a Reform vote or a Green vote.
The second chart shows the correlations between Reform and Green voting in 2024 and various socio-economic characteristics in the 632 constituencies in Britain. For example, the correlation between Reform voting and Muslim religiosity was negative (-0.48) for Reform and positive for the Greens (+0.20). In other words, many Muslim voters in a constituency weakens support for Reform and boosts it for the Greens.
Correlations with voting Reform and Green in the 2024 general election in 632 constituencies in Britain:
In addition, the presence of many non-white residents and people in professional occupations in a constituency helps the Greens and weakens Reform. In contrast, constituencies with a lot of people over the age of 65 or who think of themselves as “English” (as opposed to British) helps Reform and weakens the Greens.
Socio-economic data in Gorton & Denton and Runcorn & Helsby:
Gorton and Denton has more professionals and very many more non-white people and Muslims than Runcorn & Helsby, so we can expect a boost for the Green vote. In addition, it has fewer over 65s and English identifiers, which again helps the Greens.
This means that Reform is unlikely to win the by-election since the opposition to Labour will be divided between them and the Greens instead of it all going to Reform, as in Runcorn and Helsby. The Greens could win the by-election, but it is more likely that Labour will win because of the divided opposition.
This article is republished from The Conversation under a Creative Commons license. Read the original article.
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