GE ’24: Lagan Valley Constituency Profile…

This was the seventh most vulnerable Westminster constituency in Northern Ireland in 2019, with 6,499 votes separating the winner, Jeffrey Donaldson (DUP) from Sorcha Eastwood (Alliance). Donaldson held the seat since 1997.

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The changes made to the constituency boundaries last November were not substantial, although they have the capacity to make the constituency more marginal still.


Johnathan Buckley, DUP

Robbie Butler, UUP

Patricia Denvir, Green

Sorcha Eastwood, Alliance

Simon Lee, SDLP

Lorna Smyth, TUV

Candidates’ Electoral History

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Vote shares by designation

There were no changes to the boundaries between 2010 and 2023.

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Please note that some Local Government electoral areas cross constituency boundaries which means that the LG figures have been estimated.

The trends are clear. Unionists have declined steeply, falling just below 60% last year in the Council elections. Others have grown substantially, while nationalists have trended up gently.

Tactical voting has become very marked in the last two Westminster elections, and the underlying development in designation support can best be seen by excluding them. This shows the trends to have been more consistent than the first chart makes them appear.

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This shows unionist down nearly 16% points, Others up around 12% points and nationalists up 3% points.

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Westminster elections do not generally draw an increase over Assembly elections here. Will that be different this time?

Vote share by party in Assembly and Local Government Elections

Again, the underlying strength of the principal parties within a constituency can best be understood by looking at their performance free from the distortions of Westminster elections.

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The Greens have contested each of these elections, the only other party to do so, averaging 1%. Otherwise, various unionist parties and independents clock up 2% to 4% between them in Council elections. NI21 secured 8% in 2014.

The DUP has trended down 18% points over the period, and the UUP 2%. The TUV is up 1%.

The Alliance trend is up 16%.

The SDLP has remained flat, while Sinn Féin is up 3%.

Vote share in Westminster elections

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The boundary changes

Calculating the effects of changes to constituency boundaries is not straightforward since there is no record of precisely how past votes for each party were distributed geographically. Necessarily this involves estimates and assumptions, and these may differ. For many years the UK media have all used the calculations provided by two academics, Rallings and Thrasher, to provide a notional result of how each constituency would have voted at the previous general election if the latest boundaries had been in force. For Northern Ireland their inputs are provided by Nicholas Whyte. These will be the base from which the media will report voting swings when constituency results are declared.

I used different assumptions for my own calculations of the notional vote which resulted in slightly different outcomes. In the following chart the Actual result in 2019 is compared with my estimate and the R&T estimate.

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As can be seen the principal difference is that R&T gives a bit more to Sinn Féin and shows no dip in the DUP.

This gives different notional majorities for 2019.

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In addition to money, the other key resource for an election campaign is the level of constituency work running up to the campaign, and the manpower available in the campaign itself. When it comes to constituency work MP’s and MLA’s have the advantage of an allowance for constituency offices and for a staffing. The amount of staffing money is specified, but MP’s and MLA’s can choose to allocate it to fewer higher-paid staff or a greater number of lower-paid staff.

When it comes to manpower for canvassing and leafleting a party’s elected representatives normally form the core of the group available. Party’s may also choose to bring in helpers from neighbouring constituencies which they have no hope of winning.

The Index Total for each party gives some idea of the relative strength of each party locally.

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The Alliance resource is greatly increased since the last Westminster election, while the SDLP’s loss of its MLA will have greatly reduced its perceived presence in the constituency.

The UUP has also suffered from losing half of its Councillors. This could be of benefit to either, or both, of Alliance or the DUP.

It must be noted that the DUP index could over-represent the DUP resource, given the importance of their MP to the rating. But that MP is Jeffrey Donaldson. 27 years of accumulated personal contact with constituents has been wiped off the plus side of the DUP ledger, to be replaced with a new candidate from outside the constituency. And nobody knows whether the association with Donaldson will be a millstone around the party’s neck, or viewed as totally irrelevant by all those who voted DUP last time.

There is no TUV elected representative in the constituency. However, they have contested all elections in the constituency, bar the 2017 and 2019 Westminster, demonstrating some continuous level of local organisation.

Factors possibly assisting the DUP

14.3% points ahead of Alliance at the last election.

Absence of Conservative and Independent unionist candidates could add up to 2% points to the DUP share.

Could TUV Reform UK intervention assist DUP to squeeze up to 4 or 5% points from the UUP vote as it did in 2015?

Lack of local TUV resources could limit its ability to take votes from the DUP.

Factors possibly harming the DUP

The TUV candidate could subtract up to 9% points share from DUP. At the 2022 Assembly vote it had a 7% share. In the Westminster election in 2010 it took 9%, and in 2015 the TUV and UKIP achieved 10% between them. The latest LucidTalk poll shows the TUV on 5%, in the same ballpark as the 6.2% they scored in the Assembly election in those constituencies that they are contesting this time. Watch out for their next poll just before the election to see if they hold, grow or fade.

Total unionist vote decline. Between 2019 and 2023 there was a 6 or 7% point drop, depending on whether you measure the decline from the 2019 Council or Westminster election. This could subtract a further 3 to 4% points from the previous DUP share.

Factors possibly assisting Alliance

Absence of Sinn Féin from the contest, and loss of SDLP resource since the last election. Could add 1 or 2% points to Alliance share.

Extra MLA and Councillors resource since 2019.

Jeffrey Donaldson court case. Might shift some former-DUP voters to other parties or make them less motivated to turn out.

There are many variables in this particular constituency, and a big Donaldson-shaped unknown. Ignoring Donaldson, the balance of other probabilities suggests that on a bad day for the DUP and a good day for Alliance the two parties could be neck and neck.

But then you can’t ignore Donaldson, whose next court appearance will be in the headlines as the polling stations open.


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