these are the races to watch

As the country prepares for elections, all eyes are on the bellwether constituencies that historically reflect the broader national mood.

Where will this election be won or lost? Which constituencies hold the balance of power? And where are the key constituencies located?

In this election, answers are harder to come by than usual, as new borders were drawn, meaning that 585 out of 650 constituencies have changed shape since the last election. Some have become larger, others smaller, and some have been split into several parts with no obvious ancestor.

Because residents are voting in new geographic formations, we have only a limited understanding of the political context in which many of this year's elections will take place.

But to shed light on this issue, we have undertaken a major new data collection exercise and redistributed past election results since 1997 according to the new constituency boundaries, using population figures of 189,000. census output areas each of which contains between 100 and 625 people. This unique data provides insight into how residents in current constituencies have voted over time and which party has historically been more popular in each election, starting with Tony Blair's first landslide in 1997 and continuing. ending with Boris Johnson's emphatic victory in 2019.

The 10 best indicators

Although the country has changed politically a lot over the last seven elections, there are 55 swing constituencies, where people have consistently followed national trends and voted locally for the same party that sits in 10 Downing Street. Of these, 52 are in England and three are in Wales.

Some of these seats will be easier for Labor to win than others. In Hendon, London, Labor was just 8 percentage points behind the Conservatives in 2019. But in Cannock Chase, Staffordshire, Labor faces a tougher task. Although residents supported Tony Blair's New Labor in 1997, 2001 and 2005, residents' support for the Labor Party fell from 55% in 1997 to just 25% in 2019. The Conservatives won 68% of the vote in 2019 , making Cannock Chase one of the safest. Conservative seats in the country (47th out of 650). If Labor ends up winning, the Conservatives will have a very bad night.

Table 1 zooms in on the top ten constituencies, where local residents' vote share has most closely reflected Conservative and Labor vote shares nationally over the past 27 years. In every election since 1997, the balance of opinion among these residents has closely reflected the national result.

Local support for election winner, 1997-2019

What happened in these places could therefore be seen to have offered a snapshot of the wider political mood of that era. Residents of these constituencies may well find themselves in high demand for vox pops and focus groups in 2024.

The 338 seats that have not changed for 27 years

In contrast to these barometers, some constituencies have been remarkably resistant to political change. Residents in 338 constituencies have consistently voted for the same party in the last seven general elections. Of these, 165 voted consistently for Labour and 168 for the Conservatives.

The most loyal Conservative residents are those in South Holland and The Deepings, Lincolnshire. Here, the estimated Conservative vote has averaged 60% over the last seven general elections. John Hayes, who has held this seat throughout this period, should therefore feel confident.

The most loyal Labor residents are those in Liverpool Walton, where the average Labor vote is 75%. Dan Carden, elected for the first time in 2010, will surely want to have a chance of being re-elected as a deputy.

The ultra marginal and the ultra volatile

Another group of districts has consistently produced very close verdicts, with victory margins averaging 6 percentage points or less over the past seven elections.

Top 10 most competitive districts, 1997-2019

Of these, Eastbourne, on the south-east coast, is very interesting. On average, he produced the closest verdicts, with a very close vote between the Conservatives and the Liberal Democrats. If past behaviors are repeated, the result in these places could again be disaster.

Residents of some other constituencies have shown massive fluctuations in their support in different elections. Table 3 shows which places have been the most unstable over the past 27 years.

Blaenau Gwent and Rplomby, a new Welsh constituency created from parts of four others, sets the stage for volatility. The voters who now make up this district have shown strong support for independent candidates over the years. Peter Law, for example, was elected as an independent MP in the former Blaenau Gwent constituency in 2005, after resigning from the Labor Party in protest against all-female shortlists. The local party, Blaenau Gwent Peoples Voice Group, also polled well in the area in the mid-2000s.

Top 10 most volatile electoral districts, 1997-2019

Wyre Forest, in the Midlands, saw a surge in support for independent candidates, such as Richard Taylor, who protested against the closure of Kidderminster Hospital's A&E department. Elsewhere, some of the places where volatility has been highest in recent elections are where UKIP briefly burst onto the scene in 2015. Clacton, in Essex, witnessed the UKIP's only success UKIP, when Douglas Carswell won the UKIP candidate seat in 2015. With Nigel Farage vying for the seat this time, I'm hoping for a similar performance.