How could Sturgeon's departure affect the next general election?

If the SNP appoints a significantly less popular leader, the party stands to lose a lot of seats in Westminster

February 24, 2023
The next SNP leader may not be as popular with the Scottish electorate as Nicola Sturgeon. Photo: PA Images / Alamy Stock Photo
The next SNP leader may not be as popular with the Scottish electorate as Nicola Sturgeon. Photo: PA Images / Alamy Stock Photo

The facts have not yet changed; so I have not yet changed my mind. But they might; and if they do, I will.

In a recent analysis for Prospect I looked at the votes Labour needed to win the next election. On a uniform swing, I estimated that Labour needs a lead of 6 per cent to be the largest party and 13 per cent to win an outright majority. With tactical voting on the same scale as in 1997, the winning posts are 1 per cent and 10 per cent respectively.

Those calculations assumed that the SNP would maintain their recent poll rating in Scotland; Labour, replacing the Conservatives as the second largest party, would gain a handful of seats. Could Nicola Sturgeon’s resignation as Scotland’s first minister make a real difference, not just to Scotland’s politics, but to the coming UK general election?

The most recent polls suggest little change to party support since Sturgeon’s decision to quit. But these are early days, and there are already signs that the contest to succeed her could be divisive. So things may change. And if they do, the operation of our first-past-the-post (FPTP) voting system could make election night even more dramatic than normal.

Here are the key numbers. With thanks to the Electoral Calculus Website, I have looked at how different voting outcomes in Scotland could translate into seats at the next election. These estimates take account of the new boundaries, which reduce Scotland’s total from 59 seats to 57.

Let’s unpack those numbers. Had the last election been fought on the new boundaries, it is likely that the Liberal Democrats would have lost two seats (Fife North East and Caithness, Sutherland & Easter Ross) which they won on the old boundaries with small majorities. The other parties would have won the same numbers of seats.

Since 2019, the Conservatives have lost ground, while Labour has improved its position—as in England. The latest polls show Scottish Labour on around 30 per cent—up 11 points. This would give Labour six extra seats: handy but not earth-shattering.

What, though, if the SNP starts to slip following Sturgeon’s departure? This is where things get interesting. FPTP tends to reward parties with more than 40 per cent support and punish those that slip below 30 per cent. At the last election, SNP voters outnumbered Tory voters by less than two-to-one (45-25 per cent), but SNP MPs outnumbered Tories by eight-to-one (48-6). 

However, between 30 and 40 per cent, small movements in votes mean big movements in seats. So, while current polls would give Labour only seven seats, it would be close behind the SNP in many more. A further swing of just two points from SNP to Labour would cause five further seats to change hands. On a four per cent swing, that number jumps to 13. 

Should Labour draw level with the SNP, the chances are that Labour would actually overtake the SNP as the party with the largest number of Westminster MPs (28-20). How come? The SNP’s support is relatively evenly spread. This has been an advantage during the era of SNP dominance, but becomes a disadvantage if that dominance ends. Labour, with its concentration of support in the central belt, converts votes into seats more efficiently when support for both parties is in the mid-30s.

Plainly, if Labour is able to advance significantly in Scotland, it will affect what happens at the coming general election. Labour has suffered grievously from its collapse in Scotland after 2010. It’s the main reason why Labour has needed a big lead over the Tories in the Britain-wide polls to regain power at Westminster. The more Labour can recover in Scotland, the less daunting its task in England and Wales. As a rule-of-thumb, every five extra seats that Labour gains from the SNP in Scotland reduces by its target for victory at Westminster by one percentage point. So, if Labour wins an extra 15 Scottish seats beyond the seven indicated by recent polls, Labour will become the largest Britain-wide party with around a three-point lead in the popular vote instead of six, and an outright majority with a 10-point lead instead of 13.

Add in tactical voting, and Labour could win an overall majority with a seven-point lead instead of 10—and might even be able to become the largest party with slightly fewer votes than the Tories.

For afficionados of election-night drama, this prospect adds an extra edge. If the SNP and Labour end up both with their percentage voting support in the thirties, a dozen or more seats would be too close to call on the basis of pre-election polls or the exit poll unveiled at 10pm on election day. That would be on top of the margin of error for seat numbers in England and Wales. Unless either Labour or the Tories win a substantial majority, currently an improbable prospect, we might not have a clear idea until breakfast on the morning after election day of how the new parliament will operate—and, just possibly, not even then.