The period of modern industrialisation is commonly characterised by gradual democratisation through enfranchisement and intra-elite competition between traditional landlords and emerging capitalists. This raises the question of whether the redistribution of de jure political power via suffrage expansion can catalyse the transition of intra-elite power structures, as reflected in political representation. This study explores the impact of suffrage extension, induced by the wartime tax increase in Japan during the mid-1900s, on the occupational composition of the House of Representatives. Employing a difference-in-differences approach, I demonstrate that the expansion of the electorate led to a significant decline in the seat shares of agricultural landlords, who initially constituted the dominant occupational group in the House. In consideration of the historical context, the overall findings suggest that suffrage extension likely played a crucial role in diversifying House politics away from a landlord-centred system.