We analyse the importance of legitimacy on public policy support by comparing how drivers of public policy attitudes evolve across the policy process consisting of the input (the processes forgoing acquisition of power and the procedures permeating political decisionmaking), throughput (the inclusion of and interactions between actors in a governance system) and output (the substantive consequences of those decisions) stages. Using unique panel data through three phases of the implementation of a congestion tax in the Swedish city of Gothenburg, we find that legitimacy is indeed important in explaining policy support. Moreover, we find a lingering effect where support in one phase depends on legitimacy both in the present and in previous phases. Hence, our study takes us one step further on the road to understand the complicated dynamic mechanisms behind the interactions between policymaking, policy support, and the legitimacy and approval of politicians and political processes.