There are three sets of conditions for a process of regional integration to develop: demand, supply and inertial conditions. Demand conditions grow out of higher levels of regional interdependence, as transnational transactors perceive that cross-border activities are too costly and request national or supranational authorities to lower transactions costs through cooperation, coordination and, eventually, integration. Supply conditions refer to regional leadership, understood as the capacity and will of one or more actors either to pay a disproportionate share of the costs required by the regional undertaking (usually member states) or to provide monitoring, enforcement and regional coordination (usually supranational agencies). Inertial conditions take the form of demand or supply conditions that become institutionalized, locking in previous agreements and creating pathdependent effects -which may protect the integration process in times of declining demand or supply conditions, but may also turn it too rigid. In Mercosur, demand conditions are low, supply conditions are mostly inactive and very few inertial conditions have been created. This paper evaluates the current state and likely prospects of the bloc by singling out the areas in which these conditions are more likely to develop -or contract. The conclusion stresses the role of direct presidential involvement in deepening, enlarging and institutionalizing Mercosur -or failing to do so- and calls attention to the changing balance between fostering and administering interdependence.