Tweeting for solidarity

Digital and social media are reshaping the repertoires of contemporary labour activism, as trade unions increasingly use these platforms to mobilise members and contest managerial power. Drawing on the concepts of collective and connective action, affective publics, and distributed leadership, this article examines how the University and College Union, affiliated activists, and supporters used Twitter during a boycott of marking and assessment duties in the UK, situating the case within a broader shift towards hybrid, digitally mediated mobilisations. Based on a dataset of over 10,000 tweets and retweets collected during the boycott's initial phase, the study adopts a mixed-methods design, combining GenAI-assisted computational analysis of user activity, engagement, and network structure with thematic analysis of original tweets. Findings reveal a leaderful mobilisation in which collective and connective dynamics are intertwined and bridged by affect: national union accounts provide coordinating frames, branches translate these into context-specific action, and members and activists personalise and circulate messages through storytelling. While Twitter proved effective for information-sharing, solidarity-building, and rapid mobilisation, the analysis also identifies missed opportunities for strategic messaging diversification, broader stakeholder engagement, and dialogic interaction. By outlining how institutional structures and digital publics jointly shape mobilisation, bound together by affect, notably outrage, the paper advances theoretical debates on digitally mediated union activism. As a further contribution, it demonstrates the value and limitations of integrating GenAI tools in social media research