Despite the hopes that information and communication technology (ICT) would revolutionize democratic participation, evidence suggests that e-participation systems designed for consultation and dialogue between citizens and governments often fail to achieve the expected objectives and levels of take-up. E-participation research has identified a number of success and failure factors but lacks analytical frameworks explaining why and how failures occur. Such frameworks are available in information systems (IS) literature but lack an account of the particularities of e-participation. Combining insights from both domains, this paper proposes to conceptualize e-participation systems as innovation processes characterized by uncertainty and change, and to focus on studying systems' interactions with their context and stakeholders to understand why certain outcomes occur. Applying this approach to the case study of the Estonian e-participation portal Osale.ee, the paper concludes that e-participation systems face three-fold challenges: those typical to IS projects, those emerging from the public sector context, and specific challenges that emanate from the complex context of democratic participation. This complexity makes e-participation systems prone to fail and requires them to be managed as a process of learning and adaptation rather than a static technological product.