Public engagement has been one of the most prolific fields of democratic practice in the last two decades thanks to the rapid dissemination of a wide variety of participatory tools across governments, public sectors and countries. It includes conventional consultative forums like public hearings, advisory committees or neighborhood councils as well as democratic innovations like participatory budgeting, deliberative polls, citizen assemblies, and civic intergroup dialogue meetings-all intended to foster participatory democratic processes. With the development of public engagement, the work of designing and organizing these participatory processes is increasingly entrusted to public engagement practitioners (PEPs) (Lee 2015).Little attention has been paid to the interactions between PEPs and sponsors-a kind of asymmetrical relationship in which the sponsor is the most powerful actor. The challenges PEPs face in their mediation with sponsors can undermine their ability to implement fair and open dialogue processes. This aspect concerns not only the individual capacity of PEPs to handle abusive requests from sponsors but also the context in which the public engagement industry is developing. In this New Frontier article, we propose four research avenues to open up the "black box" of public engagement and understand the conditions inherent in establishing participatory arrangements.