This article examines the extraordinary political swing that occurred in the Durham coalfield in the 1931 general election. Having won all eleven county seats in 1929, Labour lost all but two in 1931. This was despite the dominance of the coal industry, the strength of the miners' union, and the increasing pre-eminence of Durham's Labour organization. While the circumstances of the election certainly motivated a traditional anti-socialist base, the article suggests that previous explanations have failed to acknowledge the extent to which mining constituents may also have been responsible for the result. Rather than any uniform political identity amongst the mining community, it finds that allegiances were fluid and complex, swayed by factors such as political charisma (particularly with regard to Ramsay MacDonald, re-elected at Seaham), specific local concerns, and paternalistic loyalties. In doing so, it reveals the fragility of the Labour Party's appeal even amongst its ‘core’ supporters. The National success in 1931 demonstrated that Labour's dominance in Durham remained recent, limited and as yet provisional, a finding that has significant implications for the wider picture of Labour's national advance, revealing that Labour's progress in the inter-war years was conditional and erratic even in its most ‘natural’ strongholds.