Here's something you don't see very often – a post that's not about the EU referendum! Sadiq Khan’s victory in the London Mayoral election has left a vacancy to be filled in his former London seat of Tooting. Even 85% of NCP followers (according to my voodoo poll) had forgotten about it:

Time to own up. Are you so caught up in the euref that you'd forgotten there's a Westminster by-election this week? — NumbrCrunchrPolitics (@NCPoliticsUK) June 11, 2016

But there is a by-election, and it’s quite a peculiar seat. Since being created in February 1974, it has only ever been held by Labour, with the Conservatives second on every occasion, and no other party ever polling more than 20% of the vote. The closest the Tories have come to taking the seat was in 1987, the Tories’ high watermark in the capital, when Tom Cox held on by just three points.

What’s fascinating is what has happened since. In 1987, the Conservatives won London by 13 points (2 more than nationally), compared with a 9-point Labour win in 2015 – a swing of 11%. Helped by favourable demographic trends, the swing in Tooting since 1987 has been just 1%. The Tories continue to eye this seat.



But they are unlikely to take it today. This seat is a straight red-blue contest – in 2015, no other party held its deposit, with the Greens coming third on 4.1%. This kind of seat, almost without exception, swings towards the opposition in a by-election. The only time since 1960 that a governing party has gained a seat in a by-election was in neighbouring Mitcham and Morden, during the Falklands war in 1982. Not only was it a very strong point in history for the Conservatives, but additionally the split opposition resulting from Labour incumbent Bruce Douglas-Mann’s defection to the SDP allowed Angela Rumbold to take the seat for the Tories on a reduced vote share.

Clearly the current situation looks nothing like 1982. The only wild card is the EU referendum and how it might impact turnout. Has it increased political engagement, or will people stay home knowing that they have to vote again a week later? And who benefits? All psephologically interesting, but probably academic. Any result besides a Labour hold would be extraordinary.