We present a theory that links variation in aggregate levels of political knowledge across countries and over time to corresponding differences in the political context in which voters become (or do not become) informed. Specifically, we argue that the level of partisan left-right knowledge in a given context ultimately depends on how useful the left-right metaphor is for organizing, simplifying, or otherwise facilitating voters’ understanding of political processes. Using survey data on the distribution of left-right knowledge in 59 different contexts (in 18 countries), our analysis reveals that voters understand the relative left-right positioning of parties to a much greater degree when these positions are important predictors of the composition of policy-making coalitions, but that variation in this knowledge does not correspond to the accuracy with which the relative left-right positions of parties predicts more narrow policy positions.