The referendum of 1 October 2017 was the dramatic peak of a five-year process whereby the Catalan government and secessionist political parties and civil society organisations gradually coordinated with the aim of holding a vote on the issue of independence. This paper provides the international reader with a condensed picture of this convoluted period and advances a preliminary assessment of its consequences for Catalan politics. We first describe the key developments of the secessionist challenge, from its inception in late 2012 to the holding of the 2017 regional election after the imposition of direct rule. Next, we examine over-time changes in political parties and public opinion in the wake of the conflict. The independence debate has triggered grassroots mobilisation and heightened tensions not only between parties but also within them, leading to a more polarised and fragmented regional party system. Trends in public opinion show that voters' positions on the issue, which are largely conditioned by ethnonational identities, have become increasingly influential for explaining political attitudes and behaviour on multiple domains.