The blue wall is a term used in British politics to describe a set of parliamentary constituencies in southern England which have traditionally voted for the Conservative Party, but generally opposed Brexit and are seen as being potentially vulnerable to gains either by the Liberal Democrats or the Labour Party. This shift was noticeable in the UK general elections of 2017 (when Labour gained Canterbury, which had had a Conservative MP since 1918) and 2019 (when the Liberal Democrats made inroads in Esher and Walton).