I'm getting to the point where I almost despair of our chances of clearing up the misunderstandings about how the STV voting system works in time for polling day on 4th May, because people are so wedded to what intuitively (but wrongly) seems 'obvious'. This morning, I posted a link on Facebook to my blogpost about how I planned to rank the eight candidates in my own ward, and within no time at all several indignant comments had been posted telling me that I was wrong to use my lower preferences on the unionist candidates. Apparently if we all just leave the unionist boxes blank, we'll help to "drive the unionist parties out of our councils" and prevent unionist councillors getting in "via the back door".
Now, listen. There is no requirement to rank all or most of the candidates, and in some circumstances (if you're lucky) you may not cause much harm if you decide not to do so. But if you think you are doing any actual good by leaving several boxes blank, you're deluding yourself. A pro-indy vote is not somehow more "emphatic" if you don't rank the unionists.
As long as you make sure that you rank every single pro-indy and non-unionist candidate ahead of every single unionist candidate, your preferences for the unionist parties will only be taken into account in one very specific circumstance - namely when only unionist candidates are left in contention for a particular seat. If a seat has to be filled, and only unionist candidates are in the running for it, how do you think you're going to stop a unionist from being elected by effectively abstaining? You can't - it's physically impossible. But what you can do is influence the outcome, and and help prevent the most objectionable unionist candidate from winning. It's possible you genuinely may not have any view at all on which unionist party is the most objectionable, and that's fine - but I do have a view, and deep down I think most of us do. If it's a straight choice between a Lib Dem councillor and a Labour councillor, I would prefer Lib Dem. If it's a straight choice between a Labour councillor and a Tory councillor, I would - just about - prefer Labour.
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There's also an anonymous commenter on this blog who has been putting out false information about how votes are transferred when candidates are eliminated - he or she is saying that if you rank the Greens first and the SNP second, only a portion of your second preference vote will transfer to the SNP if the Green candidate is eliminated. That's simply untrue - your whole vote will transfer. I don't think this is malicious misinformation - the commenter seems to be getting the procedure for eliminated candidates mixed up with what happens to 'surplus votes' from candidates who reach the quota early on and are declared elected.