Abstract
The 2016 referendum marks the start of a new era of euroscepticism in the UK, as the basic parameters of debate have shifted from EU membership to non‐membership as the central working assumption of the political system. This shift radically alters the political opportunity structure for those groups and elements that have developed in the period since the Maastricht treaty, removing the unifying and rallying calls of withdrawal and/or radical change to the EU. The achievement of Brexit thus poses an existential challenge, as individuals either demobilise or divert their political energies into other issues. While a core of activists is likely to remain, their scope for influencing public policy or even public debate will be further weakened by the centrality of creating and managing the UK's relationship with the EU to party political debate for the next decade: precisely because it is so important, we would expect many more voices to lobby government and opposition parties. This all points towards a sharp contraction in the organised base of eurosceptic groups, as well as continuing tensions about what still needs to be done in the grand project of opposing European integration.