We present a novel approach to disentangle the effects of ideology, partisanship, and constituency pressures on roll‐call voting. First, we place voters and legislators on a common ideological space. Next, we use roll‐call data to identify the partisan influence on legislators' behavior. Finally, we use a structural equation model to account for these separate effects on legislative voting. We rely on public opinion data and a survey of Argentine legislators conducted in 2007–08. Our findings indicate that partisanship is the most important determinant of legislative voting, leaving little room for personal ideological position to affect legislators' behavior.