South Down, Northern Ireland’s southeastern corner including Downpatrick, Newcastle and the Mournes, was Northern Ireland’s most Nationalist constituency at the last Assembly election (Foyle and West Belfast, normally well ahead on that score, voted in unprecedented numbers for the non-aligned People Before Politics). 62.5% of the vote elected four Nationalist MLAs, two SDLP and two SF. 30.2% 27.4% elected two Unionists, one DUP and one UUP. Alliance got 5.4% and the Greens 2.0%.

Five of the incumbent MLAs are standing again, with one retirement from Sinn Fein. The SDLP and SF are both defending two seats with 1.9 quotas; the DUP and UUP are defending theirs with 0.7 and 0.5 of a quota respectively. In 2016 there were 1.8 1.6 Unionist quotas and 3.8 Nationalist quotas, which on the face of it makes the battle not to come sixth a very close one.

Edited to add: I had missed the crucial fact that the votes cast for independent candidate John McCallister in 2016 (he had been elected as UUP in 2007 and 2011, and was subsequently deputy leader of NI21 until its collapse) largely failed to transfer to anyone, and therefore cannot really be counted as Unionist votes. Taking that into account knocks Unionists down to 1.6 quotas, which significantly changes my analysis. I’m keeping my original text below, but struck through.

Unionists tend to be better at internal transfers, so my hunch would be that the seat lost is a Nationalist one. The SDLP and SF were very close to each other last time; it will very much come down to which of them balances their votes better. SF are starting from behind on two counts – slightly fewer votes in the first place, and a long-standing incumbent retiring. On the other hand, SF have been consistently better at managing their votes, here and elsewhere. It may turn into a nail-biter.

Less so, I think on the Unionist side, provided the vote holds up overall. The TUV have swapped out well-known local figure Henry Reilly for Lyle Rea, who stood and lost in Lagan Valley last time, and the Conservatives are also standing someone, but I expect the vote for the two incumbents to consolidate, and it may prove easier for two Unionist parties to get two people elected on 1.9 quotas than for one Nationalist party to do the same. Still, there are a lot of ifs in that; we may find the second Unionist, the second SDLP and the second SF candidates all very close to each other for the final seat.

As noted above, Unionists combined will struggle to elect a second MLA here, and the UUP start from much the worse position. Transfers from non-aligned parties have tended to favour the SDLP here in the past. So it looks rather likely that the UUP will lose out, though one can’t discount the possibility of imbalance between candidates on the Nationalist side making the final counts exciting.