Whereas 19th century Belgium is traditionally framed as heavily dependent on France, this image ought to be nuanced for its political system. During what Pierre Rosanvallon named the transnational ‘proportional moment’ (1899-1914), the introduction of Proportional Representation in parliamentary elections generated a French interest in Belgium as the ‘electoral laboratory of Europe’. Arguments raised in the French Chambre des Députés were similar to those used in Belgian Parliament. The present article addresses the structural differences between the electoral debate in both states. Whereas Belgian constitutional doctrine adapted smoothly to the introduction of proportionality (Oscar Orban/Paul Errera) and held a moderate position bordering on that of Hans Kelsen, French doctrine was divided between the Parisian Adhémar Esmein, who defended the majority system as the bedrock of republicanism, and provincial professors of constitutional law, who had corporatist ideas, or were in favour of judicial review (Joseph-Barthélémy, Léon Duguit). Raymond Carré de Malberg’s condemnation of proportional representation as impossible, or as the stepping-stone to direct democracy, ought to be situated within this context.