Though the choice put to voters is between national parties, a British general election is not structured as one national contest but 650 winner-takes-all local competitions. Every campaign therefore operates at two levels—an ‘air war’ of interviews, set-piece events and national media communications where political leaders make their cases on air, in print and online, and a ‘ground war’ of door knocking, phone calls, text messages, direct mail, leaflet deliveries and targeted online communication where activists and candidates seek to inform, persuade and mobilise local voters. While the ‘ground war’ is less visible to the national media or the average voter (particularly the average voter outside target seats), it is a core part of campaigns—one which parties plan carefully and resource intensively, and which can, at least sometimes, be decisive. And in an election where local variations in party fortunes and voter behaviour were historically large—so large, indeed, that talk of ‘national swings’ conceals as much as it reveals—the ground game may have mattered more than usual