Ideological synergies as proxy for coalition efficiency in presidential systems

Scholarship on coalition governments highlights the distribution of payoffs along coalition members as the factor that holds coalitions together. In presidential systems, parties from various ideological positions join and leave coalitions throughout a term to sustain – or obstruct – a government’s capability of passing bills. Nevertheless, the effectiveness of ideologically homogeneous coalitions in comparison to those more heterogeneous in sustaining a government and efficiently approving policies of presidential interest is not clear. I argue that coalition parties more ideologically distant to the president’s party are more loyal due to the access to office perks. I also theorize that these coalition parties succeed in obtaining more portfolios in exchange for congressional support, whereas those closer to the president do not have enough leverage to negotiate office goods. To test these hypotheses, I examine the approval rate of bills of presidential interest based on the coalition members’ ideological position and the number and salience of portfolios each coalition party received. I investigate coalition behavior in nine South American countries between 2010 and 2020 to test whether ideological position, to be obtained from a text analysis model on lawmakers’ speeches, is a predictor for coalition loyalty in multiparty presidential systems.