Many standard models of political institutions frame outcomes as a function of the preferences of key decision makers. However, these models, and the empirical analyses they inspire, typically assume decision makers can infer the identities and ideological locations of other decision makers without error. Here, we reveal the substantive importance of this assumption. We show that partisan sorting, a common cause of polarization, can result in reduced uncertainty about the ideologies of key decision makers and the identities of key pivots. When we incorporate estimates of pivot uncertainty into empirical models of executive order issuance, we find lower levels of uncertainty are associated with higher rates of policy-relevant executive order issuance. These results have implications for the study of polarization and the use of models of institutions in political science.