The Labour Party’s showing in the by-election in Chesham and Amersham, in Buckinghamshire - down from 12.9% to 1.6%, 622 votes, about the same as the number of Labour members in the constituency! - was certainly very poor. Contrary to widespread suggestions, however, it is not unprecedented.
In the 2016 by-election in Richmond Park, South West London – also won by the Lib Dems on a huge swing from the Tories – Labour’s vote share fell from 12.3% to 3.6%. There have been other similar by-elections – for instance in Orpington in 1962, when Labour went from second to badly third and the Liberals went from third to win. That was two years before the first Labour general election victory in 13 years, in 1964, followed by a landslide Labour victory in 1966.
In the 2017 general election, the Labour vote in Richmond Park recovered a bit from the 2016 by-election, though not to its 2015 level. More widely, across the country, however, the Labour vote increased substantially and the Tories lost their majority. The Chesham and Amersham result should be concerning for Labour and the left - but it does not mean “game over”.
The difference is that in 2016-7 there was a sizeable and mobilised Labour left, which is now much more demobilised. Labour did badly in the polls (up to 20% behind) right up until the Tories called a general election in mid-2017, and the Lib-Dems did relatively well in the polls over that same period. Then Labour pulled together with a relatively hard-hitting tax-the-rich, reverse-the-cuts manifesto, got a sizeable number of campaigners out onto the doorsteps, and surged. Labour can surge again, but only by an active effort to convince voters, not by endless triangulating.
Despite Starmer’s clear victory in the Labour leadership election a year and half ago, there is now very little enthusiasm for his leadership and policies among Labour members. By pandering to socially regressive, nationalistic views while having very little to say about living standards, workers’ rights and social provision, Labour is dissipating the left-wing core of its 2019 support. That is interacting with wider and longer-term trends towards the dissipation of Labour's support.
Whether the particularly sharp fall in the Labour vote in Chesham and Amersham, compared to similar by-elections in the past, is due to this disillusionment among Labour members and supporters is hard to know (though the Green vote holding up much better would suggest it is in part). What seems clear is that Labour will not turn things around without an enthused left-wing base of support.