Ultimately, the outcome of any democratic election depends on how voters decide to cast their ballot. However, the impact of their choice also depends on how their votes are treated by the electoral system. That is likely to prove particularly the case in the Scottish Parliament election in May.
As at previous devolved elections, the battle for Holyrood will be conducted using a variant of the ‘Additional Member System’. It comes in two parts. Of the 129 MSPs to be elected, well over half will be chosen using first-past-the-post. In 73 separate constituencies, voters will be able to cast a vote for their local MSP. Whichever candidate secures most votes in each seat is elected. At previous Holyrood contests, the Conservatives, Labour, the Liberal Democrats, and the SNP have put up a candidate in every constituency, whereas the Greens have only contested a handful. It remains to be seen how many constituencies Reform will decide to fight.
The remaining 56 seats are elected using a system of proportional representation. For this purpose, Scotland is divided into eight regions, each of which elects seven ‘additional’ members. Each party puts forward a list of candidates in rank order. Voters are invited to vote for one of these regional party lists – they can vote for the party whose candidate they have backed as their local constituency MSP or for a different party. Crucially, the seven additional members are allocated to the parties such that the overall tally of seats in a region – both constituency and list – is as proportional as possible to the share of the list vote cast for each party in that region.
The constituency race
Polls taken towards the end of 2025 put the SNP, on average, at 34% on the constituency ballot, well down from the 48% the party secured at the last Holyrood election in 2021. Nevertheless, the SNP were still well ahead of its nearest rivals, that is, Reform on 20% and Labour on 16%. Trailing further behind were the Conservatives with 10% and the Liberal Democrats with 9%, while the Greens (who again may not contest many constituencies) were on 8%.
Support for the SNP does not vary a great deal from one part of Scotland to another. Given the size of its Scotland-wide lead, on these figures the party is therefore likely to be ahead in most constituencies. Consequently, despite the fall in its support, the SNP might well retain all but a handful of the 62 constituency seats the party won in 2021. In that event, the outcome of the constituency contests would be highly disproportional. The party will likely have won three-quarters to four-fifths of the constituency seats on little more than a third of the vote.
A barrier for Reform and the Greens?
On the evidence of last year’s Westminster election, support for Reform could also be quite evenly spread across Scotland. But whereas first-past-the-post is generous to a party with an evenly spread vote that is well in the lead (because it comes first in most constituencies), it punishes a second (or third) placed party whose share of the vote is much the same everywhere (because it comes second or third almost everywhere). As a result, Reform might fail to win a single constituency seat – along with the Greens. In contrast, the other opposition parties – the Conservatives, Labour, and the Liberal Democrats – all have local fiefdoms that should ensure they all at least win some constituency seats.
Reform is thus likely to be especially dependent on winning regional party list seats. At 19%, their level of support on the list vote in recent polls has been similar to their 20% support on the constituency ballot. Much the same is true of Labour (16%), the Conservatives (12%), and the Liberal Democrats (9%). But, at 29%, support for the SNP on the list vote has been markedly lower, not least because those who say they would back the SNP on the constituency vote are especially likely to say they would support the Greens on the list vote. Indeed, at 12%, support for the Greens has been both four points higher than on the constituency ballot and four points up on what the party won in 2021.
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Compensation on the list?
Consequently, as at previous Holyrood elections, the Greens will be dependent on the allocation of list seats. But this time around, the single biggest beneficiary could prove to be Nigel Farage’s party. Indeed, if Reform does emerge as the second most popular in list votes, it could win sufficient list seats to become the second largest party and thus the official opposition at Holyrood.
However, under these circumstances the allocation of list seats will not correct fully the over-representation secured by the SNP in the constituency contests. The party’s likely success in those would mean that, despite not being awarded a single list seat, the nationalists will have 45% or so of the seats in the chamber, well above the party’s 29% share of the list vote. There are simply too few party list seats to reverse the SNP’s likely over-representation on the constituency ballot.
One election in two different parts
Between them, then, the two parts of Holyrood’s electoral system are likely to have a significant impact on the shape of the next Holyrood chamber. The outcome of the first-past-the-post contests could well ensure that, despite being far less popular than five years ago, the SNP remain the dominant force in the parliament. Yet at the same time, by ensuring both the Greens and Reform secure representation they might otherwise lack, the allocation of party list seats could still prove crucial. The Greens could do well enough to ensure that, together with the SNP, there is once again a pro-independence majority at Holyrood.
Meanwhile, the list part of the system opens up the possibility that Reform could become the second largest party in seats should they manage to emerge as the second largest party in votes. All of which could leave the Conservatives, Labour, and the Liberal Democrats at risk of all looking a little bit like ‘also rans’.
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