Swingometer and swing

The 'Swingometer' – a staple of election night broadcasts – was developed at the initiative of David Butler for the BBC's general election coverage of 1955. 

Butler had first developed the concept of 'swing'  the percentage shift of votes from one party to another between elections – in his statistical appendix to the first Nuffield study, The British General Election of 1945 (Oxford, 1947).

Butler then advised the BBC ahead of the first televised results programme at the 1950 election, partly inspired by the lively American election television results programme he had watched in New York in 1948. Keen to inject more facts into the coverage, he gave further feedback for the 1955 programme, learning lessons from the election broadcasts of 1950 and 1951. Eager to communicate his 'swing' model, he wrote in March 1955 of the need for 'a speedometer type device', which would display 'swing' on a dial. Butler's letter came complete with a compass-drawn, semi-circular diagram that was recognisably the first Swingometer.

The Swingometer was promptly, if briefly, rolled out as a small graphic during the May 1955 general election coverage. By the next election, in 1959, it had been inflated to the prominent chart that is better-known today and was operated by Butler himself. Butler would rarely operate it thereafter, aside from a 1965 local election programme. Over subsequent decades, the Swingometer would be better-identified with operators Bob McKenzie, Peter Snow and Jeremy Vine. 

Butler always credited Stephen Milne as the designer of the Swingometer, and indeed, the first design was Milne's creation. However, research carried out for the official biography of David Butler has unearthed the extent of Butler's role in conceiving and commissioning that original design.