Germany and New Zealand use electoral systems that are very similar to the one used for Holyrood elections in Scotland, but with one crucial difference: They add extra seats (so-called overhang seats) to the parliament until the seat distribution mirrors the second vote (i.e., if one party has won “too many” constituency seats, extra list seats will be added to make the result properly proportional). The consequence of this is that only the second vote really matters from a party-political point of view — the first vote is important from the perspective of electing specific politicians rather than others, but it doesn’t affect the number of seats won by each party. This system is quite easy to understand.
In Scotland, however, things are different. When one party dominates heavily in one or more regions (like the SNP do at the moment in most of Scotland, and like Labour used to do in the Central Belt), the other parties end up with too few MSPs because there simply aren’t enough list seats. This makes it really hard to understand the system, and it leads to a lot of frustration when people attempt to bend the system to their own advantage.
At the moment, winning constituency seats only really matters to the SNP. Of course the other parties would love to win a few because it feels good, but it won’t affect the Holyrood result in a predictable way. For instance, imagine the list result in the West Scotland region points to SNP 9, Cons 4 and Lab 4 (and for simplicity’s sake, 0 for the other parties). If the SNP win 9 (out of 10) constituency seats and the Tories win 1, it’s easy to see what happens: Labour get 4 list seats and the Tories get 3, so that the regional result ends up like it should. What if Labour take one further constituency from the SNP? The SNP then gets one of Labour’s list seats, leaving the over-all result unchanged. But what if the SNP manage to win all 10 constituency seats? Because the number of list seats can’t grow, the list will now either say Labour 4, Cons 3 or Labour 3, Cons 4 — in other words, the SNP taking one constituency seat from the Tories could actually end up losing Labour a seat. This is counter-intuitive and bad for democracy.
The real reason for the SNP’s #bothvotesSNP campaign is safety: If the SNP manage to win all constituencies on Thursday, the number of list votes is unlikely to be significant, but if they only win 60 constituencies (i.e., five seats short of a majority), they will probably get at least a handful of list seats, so long as their voters haven’t given their second vote to somebody else. However, the Greens’ relatively successful #secondvoteGreen campaign are probably causing some natural SNP voters to split their votes, and suddenly a majority isn’t certain, so I can completely understand why some SNP strategists are a bit worried. The silly thing is just that what the SNP need more than anything is that all independence supporters — SNP, Green and RISE — vote SNP with their first vote, but that’s hard to campaign for while convincing their own supporters not to split their votes.
I wish Scotland would introduce additional list seats like in Germany and New Zealand — or replace the system with a completely different one, such as the one used in Denmark. The current one is just making everybody frustrated.