Why, when and how do activist groups make public endorsements of others at particular points of time, even though they may represent different identities, advocate for different ideologies, disagree on their goals and the means of achieving them, and may even suffer negative repercussions from making such endorsements? This talk examines boundary-spanning behaviors of moderates and radicals within social movements. Existing theories, which emphasize instrumental purposes and emergent identities, fall short in explaining the timing and asymmetry of such interactions. This talk argues that moderates and radicals respond asymmetrically to an unfolding political process. Short-term events such as interactions with various institutional actors, brief windows of institutional openness, elite endorsements, and international support alter political access and audience scope, affecting how movement actors prioritize Tilly’s WUNC criteria (worthiness, unity, numbers, and commitment) before the audiences. Such shifting priorities, in turn, shape inter-faction relations. This analysis leverages original inter-organizational endorsements network and political event datasets extracted from over 730,000 Telegram posts during the 2019 Hong Kong Anti-Extradition Amendment Bill protests. Blockmodels and relational event models results show that moderates and radicals are more likely to endorse across factional lines when interactions with institutional actors signal restricted access to the polity and expose movement actors to external audiences. The findings contribute to broad discussions on boundary-spanning behaviors, inter-organizational coordination, movement dynamics, and contentious strategies.