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A Tale of Two MRPs: Can Constituency Polls Really Accurately Predict Election Results?

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A Tale of Two MRPs: Can Constituency Polls Really Accurately Predict Election Results?

According to conventional wisdom, the Multilevel regression with post-stratification (MRP) model is the gold standard for contemporary political divination.

Using a national sample of over twenty thousand participants, examining findings by constituency and using advanced statistical regression analyses, the MRP survey is there to tell us who is participating and who is not. Before the returning officer’s declaration, the MRP is there to “take time” for an individual political career before the bell is actually rung.

But is that also true?

Over the past two days, two of the UK’s largest polling companies, IPSOS (June 18) and YouGov (June 19), have published two MRP polls, both with samples of around twenty thousand participants. As such, each poll has received widespread media attention.

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Yet surprisingly little direct comparison has been made between the findings of these surveys – and this underlines the potential fragility of this polling method.

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Because while both the Ipsos and YouGov polls both predict a Labor landslide – with Keir Starmer’s party on the face of it winning 453 seats according to the former estimate and 425 seats according to the latter estimate – the predictions are often completely different if you delve into the findings at the constituency level.

Here are some key examples:

1) A breakthrough in reforms in Barnsley North?

According to the Ipsos poll, Labor is on course to comfortably reach 56 percent of the vote in Barnsley North, with Reform UK easily trailing 24 percent of the vote. Yet YouGov has very different findings. This part of South Yorkshire saw some of the best results for the Brexit Party in 2019, and YouGov only narrowly retained Labor in Barnsley North with 37 percent of the vote – compared to 34 percent for Reform UK.

2) The Liberal Democrats romping home in Tunbridge Wells?

According to YouGov’s MRP, the Liberal Democrats will comfortably win Tunbridge Wells with 40 percent of the vote, compared to 31 percent for the Conservatives. Yet the Ipsos survey from a day earlier paints a different picture. Ipsos is not so “disgusted with Tunbridge Wells” but has the Conservatives holding the seat at 35 per cent – ​​while the Liberal Democrats only get 22 per cent, almost half the level suggested by YouGov.

3) A green breakthrough in North Herefordshire?

According to Ipsos, the Green Party is ahead in their target seat of North Herefordshire, polling at 36 percent compared to the incumbent Conservatives who are on 30 percent. But wait a minute: here the picture is almost the reverse of that in Tunbridge Wells. This time, YouGov North Herefordshire’s projects will be a comfortable seat for the Conservatives, who can easily beat the Greens with 34 percent. According to YouGov, the party is in the polls at just over half of Ipsos’ figure of 20 percent.

4) Liz Truss is under serious pressure – but from whom?

According to Ipsos, Liz Truss may soon no longer harbor such warm feelings towards Reform UK leader Nigel Farage, given the sharp forecast in her Norfolk South West constituency. The poll puts Liz Truss at 31 percent, compared to 30 percent for Reform UK. Yet according to YouGov, it is Labor that poses the biggest threat to the former prime minister, with Liz Truss on 33 percent, Labor on 29 percent and Reform UK on 25 percent.

5) The SNP is advancing towards the Scottish borders?

According to Ipsos, the SNP is doing well in the three major constituencies immediately north of the English border. The pollster predicts the party will win Dumfries and Galloway from the Conservatives; In Berwickshire, Roxborough and Selkirk, meanwhile, Ipsos has an SNP poll of 33 percent – ​​just under the Conservatives’ 35 percent.

But again, the picture between the two MRP polls is clearly different. YouGov has a 42 per cent lead over the Conservatives compared to the SNP’s 31 per cent in the Berwickshire seat.

6) Labor winning the battle?

According to YouGov, Labor could make one of its most notable gains on the south coast, the retirement seat of Bexhill and Battle in East Sussex – long one of the Conservatives’ safest seats, and a constituency with the lowest proportion of younger voters in all of Britain . But while YouGov expects a Labor victory by a three-point margin, Ipsos thinks Conservative hegemony will be maintained – with the party winning by a more comfortable 7 percent.

7) And total confusion at Newton Abbot…

One of the biggest differences between this week’s two MRP polls is in the Conservative seat of Newton Abbot in Devon. According to Ipsos, the Conservatives are on 36 percent, leaving Labor on 29 percent and Reform UK in fourth place with 12 percent.

But according to YouGov, instead of a challenge, Labor is in fourth place with 16 percent of the vote. In Newton Abbot, YouGov has the Conservatives on 31 percent, while the Liberal Democrats are narrowly on 25 percent and Reform UK on 23 percent.

Can we trust MRP polls?

Over the years, the public has had reason to be skeptical of national opinion polls, the same ones that predicted a Labor victory in 1992, and an outright Conservative majority in 2017.

This election there seems little doubt about the national outcome, with all polls predicting a solid Labor landslide as party polls are double that of the Conservatives.

But where exactly Labor will win those seats, and especially how many seats the Liberal Democrats and Reform UK will win, seems much less certain.

As the story of the two MRP polls mentioned above shows, based on an average of just 35 interviews per seat, the constituency-by-constituency polls raise completely different expectations.

These seem to go well beyond a basic margin of error.

As such, the findings of an MRP poll may be useful for political parties to display in bar charts in campaign literature – but based on the very different findings in the analysis above, one may wonder whether these types of polls are worth the statistical value. paper on which they are written.

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