The present thesis examines the question of electoral system choice by means of a crisp-set Qualitative Comparative Analysis. The thesis argues for the development of a configurational comparative research strategy, making use of both qualitative and quantitative methods, in order to explain the relative influence of potentially causal explanatory factors. The study privileges the assessment of multiple conjunctural causation and causal asymmetry in leading to the adoption of proportionally representative electoral systems and the retention of majoritarian electoral systems.