Podemos emerged in the wake of mass anti-austerity protests, promising to offer a novel party form that would shake up Spanish politics. Following a rapid bursting onto the scene, however, today Podemos faces an existential crisis. Utilising data gathered via interviews with leading Podemos figures as well as cadres and activists from an array of leftist parties and organizations, this article sheds light on why and how the Podemos party-building process reached such a critical point whereby the party has been delegitimised and where it risks replacement by Sumar as the reference point on the left of the party system. The article argues that a combination of opposition pressures and a desire by leading party figures to gain as many votes as quickly as possible fostered a rapid moderation of the party’s brand. Moreover, the article argues that to pursue such brand moderation entailed a sidelining of radical voices from the party via degenerative factionalism in conjunction with oligarchization. This moderation-factionalism-oligarchization faced weak popular sector organization resistance, helping contextualise the process, and the subsequent decline in popularity and legitimacy of the party. The outcome of the process entailed a Podemos which lacked a clear party brand or organic linkages to societal organizations, leaving its very survival in jeopardy.