Government-Opposition or Left-Right? The Institutional Determinants of Voting in Legislatures

Abstract

This study uses roll-call voting data from 16 legislatures to investigate how the institutional context of politics—such as whether a country is a parliamentary or presidential regime, or has a single-party, coalition or minority government—shapes coalition formation and voting behavior in parliaments. It uses a geometric scaling metric to estimate the “revealed space” in each of these legislatures and a vote-by-vote statistical analysis to identify how much of this space can be explained by government-opposition dynamics as opposed to parties’ (left-right) policy positions. Government-opposition interests, rather than parties’ policy positions, are found to be the main drivers of voting behavior in most institutional contexts. In contrast, issue-by-issue coalition building along a single policy dimension is only found under certain restrictive institutional constraints: presidential regimes with coalition governments or parliamentary systems with minority governments. Put another way, voting in most legislatures is more like Westminster than Washington.