The turmoil in the Conservative party unleashed by Boris Johnson’s abrupt resignation from parliament has triggered three separate byelections. The first is in the former prime minister’s London seat of Uxbridge and South Ruislip, where he had a majority of just over 7,000 votes in 2019 with Labour in second place. The second is Nigel Adams’s constituency of Selby and Ainsty, a safe North Yorkshire Conservative seat with a majority over Labour of more than 20,000. The third is Nadine Dorries’s seat of Mid Bedfordshire, which has a majority over Labour of just under 25,000 votes, making it a very safe seat.
Byelections are not generally thought to be a good guide to a party’s performance in a subsequent general election. Certainly, one can find examples of parties doing exceptionally well in byelections but not sustaining the success in a subsequent general election. The classic example of this is the Liberals’ 1962 win in Orpington. It was the first victory for the party outside the celtic fringe and the party leader, Jo Grimond, claimed that it was a major breakthrough. However, the party won only nine House of Commons seats in the 1964 general election.
More recently Labour retained Peterborough in a byelection in June 2019, even though it lost just over 17% of its vote share in comparison with the previous election in 2017. The Conservatives lost almost 26% of their vote share, much of it captured by the Brexit party. So while Labour held on to the seat this result proved to be no guide to the general election in December of that year, which the party lost badly.
