How does the Wellingborough by-election result compare to other by-election swings?

Following Labour’s by-election victories in Wellingborough and Kingswood, we’ve seen a number of people stating that yesterday saw the second biggest by-election vote swing since World War Two.

Speaking on BBC Breakfast this morning, Labour leader Sir Keir Starmer made a similar claim, saying: “These were huge swings to Labour, the Wellingborough one was the second biggest swing in a by-election since the Second World War.”

These claims relate specifically to by-elections won by Labour. It is true that Wellingborough saw the second largest post-war by-election swing in favour of the Labour party, and one of the largest by-election swings seen overall in the post-war period, but a number of other by-elections in that period have seen higher swings to other parties.

Vote ‘swing’ is a way of measuring the change in voter support between two parties, and is usually expressed as a positive or negative percentage point change calculated from the change in each party’s percentage share of the vote from one election to the next.

Yesterday’s by-election in Wellingborough saw a 28.5% swing from the Conservatives to Labour. The only post-war by-election to see a higher swing to the Labour party was the 1994 Dudley by-election, which saw a 29.1% swing from the Conservatives to Labour.

According to the House of Commons Library, the highest post-war by-election swing to any party took place in Bermondsey in 1983, when the vote swung from Labour to the Liberal party by 44%.

More recently, the 2014 by-election in Clacton saw a 41% swing from the Conservatives to UKIP—though it’s worth noting that this by-election was triggered by then-sitting MP Douglas Carswell resigning his seat in order to stand as a UKIP candidate, having defected from the Conservative party.

During this Parliament alone, larger swings than that seen in Wellingborough have been recorded in by-elections in North Shropshire, Tiverton and Honiton and also Somerset and Frome, with swings from the Conservatives to the Liberal Democrats of 34%, 30% and 29% respectively.

The Conservative to Labour swing seen in Wellingborough is also larger than any swing in the other direction in by-elections since World War Two. The largest Labour to Conservative by-election swing took place in Walsall North in 1976, where there was a 23% swing to the Conservatives. This followed a by-election triggered by the resignation of John Stonehouse from Parliament. He had been sitting as an English National Party MP after resigning from the Labour party while facing a number of criminal charges, and having attempted to fake his own death.

Image courtesy of Elliott Stallion