Central theories of public policy imply that lobbying is demand-driven, meaning highly responsive to the levels of access that political gatekeepers offer to interest organizations. Others stress drivers at the supply side, especially the severity of disturbances which affect an organization's constituency. We test these central arguments explaining lobbying activities in a comparative survey experiment conducted in 10 polities in Europe. Our treatments vary the severity of two types of external threats faced by interest organizations: (1) barriers that restrict their access to decision-makers and (2) disturbances that compromise an organization's interests. We operationalize these threats at the demand and supply side of lobbying based on an (at that point) hypothetical second wave of COVID-19. Our findings show that while severe access barriers trigger a flight response, whereby groups suspend their lobbying activities and divert to protest actions, higher disturbances mobilize groups into a fight mode, in which organizations spend more lobbying resources and intensify different outside lobbying activities. Our study serves novel causal evidence on the important dynamic relationship between policy disturbances, political access and lobbying strategies.