Understanding voter preferences in proportional representation (PR) systems is an essential first step towards understanding candidate selection and behavior. We unearth conceptual challenges of constructing a theory of sincere voting in PR elections. Using a rich but tractable framework, we propose a foundational theory of voting behavior in list PR systems. We show how voters’ expectations about the election outcome shape the relative salience of different candidates on a party’s ballot and ultimately determine their induced preferences over a party’s list. Our framework shows how voters allocate their attention across different ranks on a party’s ballot, and how this depends on each party’s relative popularity.