Economic voting theory posits that voters reward or punish governments based on their economic performance. While institutional clarity of responsibility has been shown to condition this relationship, less attention has been paid to how perceived policy differentiation between parties shapes it. We develop a unified framework linking these two informational conditions through the concept of clarity of alternatives: the degree to which voters perceive clear, ideologically distinct policy positions between incumbents and challengers. We, then, argue that voters' capacity to hold governments accountable is shaped by both institutional clarity of responsibility and clarity of alternatives, and derive testable implications for how perceived party separation, positional precision, and a composite index of the two condition the economic vote. Using CSES data across 41 democracies and 100 election studies (1996--2021), we find that perceived party separation and the composite clarity-of-alternatives index amplify economic voting. However, rather than reinforcing each other as the theoretical model predicts, clarity of responsibility and clarity of alternatives partially substitute: programmatic party differentiation proves most consequential for accountability in institutionally diffuse settings where responsibility is hardest to assign. These findings extend existing models of retrospective voting and carry implications for understanding party strategy and democratic accountability.
