GE ’24: Foyle Constituency Profile…

This was the safest Westminster constituency in Northern Ireland in 2019, with 17,110 votes separating the winner, Colum Eastwood (SDLP) from the second placed Elisha McCallion (SF). McCallion had won the seat in 2017. Prior to that the SDLP had held the seat at every election since the constituency was created in 1983.

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The changes made to the constituency boundaries last November were not substantial.


John Boyle, Aontú

Sandra Duffy, Sinn Féin

Colum Eastwood, SDLP

Rachael Ferguson, Alliance

Shaun Harkin, People Before Profit

Anne McCloskey, Independent

Gary Middleton, DUP

Janice Montgomery, UUP

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 most obvious feature of this chart is the peaks on the green line showing how each Westminster election brings a significant jump in nationalist share. This coincides with very clear dips in the Other line. There are also dips, small almost imperceptible ones, in the unionist line until the 2019 election when the dip is very noticeable. That, as we shall see, is the effect of tactical voting for the SDLP.

Changes in the true underlying strength of each designation can best be seen by excluding the Westminster elections.

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This shows that nationalists have lost 10% points of share over the period. The big dip came in 2016 when People Before Profit designated as Other, as a result of which their votes were moved into the Other column from then on.

In fact the redesignation of PBP accounts for all but 2% points of the nationalist decline, as can be seen in the graph below which shows the counterfactual if PBP had designated as nationalist, but retained the same vote levels.

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Vote share by party in Assembly and Local Government Elections

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In addition to those above, there is the sporadic appearance of other parties which never get above 1 or 2%, with the exception of Aontú which took 3% at the 2019 Council elections and 4% at the most recent Assembly and Council elections.

The most important lines on the chart, and the most significant for this election, are the top two showing the interaction between the SDLP and Sinn Féin. For most of the period the two jockeyed for the top position, first one up then the other. While the Sinn Féin vote share has been quite volatile, it has actually varied around a flat trend line. The SDLP, however, has been on a gentle slope downward throughout the period, until its dramatic fall in the last Council elections to 25%. That fall actually takes it 3% below its trend line. Over the period it has trended down by 7% points.

The lower half of the chart is very crowded, so I have reproduced that part below at a larger scale. It is relevant to this election due to the high levels of tactical voting.

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The DUP has trended downwards by 7% points, while the UUP is up by 4%.

People Before Profit peaked in the 2016 and 2017 Assembly elections. The retirement of Eamonn McCann appears to have had some impact, but they have still managed to achieve a 3% trend growth over the period. Alliance has grown by 5% points.

The brown spot and lines represent votes for Independent nationalist candidates. Where their votes go in the more restricted contest of a Westminster election could be critical. The transfers from the Independent candidates in the last Assembly and Council elections demonstrated no significant preference between SF and the SDLP.

However, the Independent nationalist standing this time, Anne McCloskey, adds an additional complication to the mix. There is no transfer information from her previous elections to indicate whether she will take more votes from SF or the SDLP, indeed she might cause more damage to Aontú given her previous association with that party.

Vote share in Westminster elections

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This chart illustrates the dramatic swing to the SDLP from Sinn Féin at the last election.

Since then, Sinn Féin have overhauled their local party, retiring the candidate who won for them in 2017 and then lost in 2019, while only three of the seven SF councillors elected in 2019 stood again in 2023.

Tactical voting

Tactical voting by unionists and Others for the SDLP in Foyle Westminster elections has grown dramatically, although it has not yet determined the outcome.

By comparing Assembly, Council and Westminster votes it is possible to arrive at a good estimate of the size of the tactical vote. In this chart the solid black line shows the actual SDLP vote, while the dotted line shows what it would have been without tactical votes.

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As you can see in 2010 tactical votes added 4% points to the SDLP share, 2% in 2015, 10% in 2017 and 13% in 2019.

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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This gives different notional majorities for 2019.

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It appears that the changes could be slightly beneficial to Sinn Féin.


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 SDLP lost two Councillors recently in a dispute over the selection of the City Mayor, one in Foyleside and one in Sperrin (part of which lies within the constituency). The index reflects these losses. Despite this they remain in a strong position since they now enjoy the advantage of incumbency which was Sinn Féin’s in 2019.

It is reasonable to speculate whether the decision of the SDLP councillors to leave could be symptomatic of morale issues within the wider local party organisation.

Factors possibly assisting the SDLP

36.3% points ahead of Sinn Féin at the last election.

Their MP has enjoyed the advantage of paid staffing for constituency case work.

Could more tactical votes be squeezed from Others and unionists? Guestimate of possible additional benefit: 1 or 2% points

Factors possibly harming the SDLP

Fall since 2019 in base vote. Comparing 2019 and 2023 Council elections this could subtract up to 6% points.

Boundary changes could subtract nearly 1% point from share.

Defection of two councillors to Independent could damage local party moral and canvassing effort.

Factors possibly assisting Sinn Féin

Rise since 2019 in base vote of 11% points comparing 2019 and 2023 Council elections.

Boundary changes could add nearly 1% point to share.

Factors possibly harming Sinn Féin

Volatility of Sinn Féin vote. It fell 5% points below trend in 2016, was 4% above in 2017, then 7% down again in 2019.

Will European and Council election in the South have reduced cross-border helpers, particularly in the first half of the campaign?

In the worst-case scenario for the SDLP their vote drops to around 40%. On the best-case scenario for Sinn Féin their vote rises to around 40%. The margin for a Sinn Féin victory is therefore narrow.

On the balance of probabilities, the most likely outcome is an SDLP hold with a much reduced majority.


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