Plain language summary: "There are few models that help us understand how external support providers work with organizational, system, and community partners to improve their efforts to implement innovative programs and practices. Existing models typically describe characteristics and features of the process but lack grounding in well-established theories of behavior and organizational change. In this paper, we theorize about mechanisms of change within the support process, which we label core practice components, and explain how their use might improve implementation efforts through shorter- and longer-term practice outcomes. We believe that our model holds promise for informing future advancements in both research and practice. Foremost, the core practice components lend themselves to behavioral definitions and thus being observed and reported in action. In research, this will allow the relationships we propose in our model to be tested and refined over time, resulting in an incremental accumulation of knowledge. In practice, a greater understanding of core practice components and their relationships to key practice outcomes offers ways to enhance training and coaching activities for external support providers. The model may also aid support providers to more effectively navigate the support process and plan more timely and effective support strategies."