Introduction: Ideal point models can map legislative voting onto ideological positions, but their application is complicated when political disagreements are driven not just by ideology, but also by governmental power dynamics. Using an anonymous survey of Brazilian legislators as a source of auxiliary data, this article develops a method to hierarchically identify the dominant ideological dimension while distinguishing it from other determinants.

Data & Methods: We analyzed roll call votes across eight presidential-legislative periods in Brazil (1985-2006). Our approach combined standard ideal point estimation techniques with auxiliary survey data on legislators' positions to isolate nonideological factors.

Key Findings: A significant government-opposition dimension was identified, independent of the ideological left-right spectrum. This dimension shifts noticeably when political parties enter or exit governing coalitions—changes that reflect presidential control over crucial resources rather than purely ideological stances.

Why It Matters: Our findings challenge conventional understandings of Brazilian legislative politics. They demonstrate how resource-dependent conflicts can override ideological voting patterns, offering a more nuanced perspective on the country's unique political landscape.