El presente artículo reconstituye y analiza detalladamente el itinerario que llevó al Partido Democrático de Chile (PD) en los últimos años del siglo XIX, al ingresar a la Alianza Liberal e incorporarse de lleno al sistema parlamentarista. Planteamos que el PD tuvo dos motivaciones básicas que se entrelazaron estrechamente y que hicieron indefectible su convergencia con la Alianza Liberal y participación en el juego parlamentarista. Uno ideológico: su anticonservadurismo y anticlericalismo; y uno práctico: la necesidad de “defender” las diputaciones obtenidas en el momento de la calificación de las elecciones por los parlamentarios, lo que los obligaba a buscar aliados. Ambos motivos se desprendían, a la vez, del carácter reformista de este partido, de su autoidentificación con el liberalismo –como su ala plebeya, más decidida y consecuente– y de su proyecto de reforma democrática del Estado oligárquico.The present article reconstructs and analyzes in detail the path that the Chilean Democratic Party (PD) took during the fi nal years of the nineteenth century, upon entering the Liberal Alliance and fully participating in the parliamentary system. The article argues that the PD had two basic motivations which were closely interwoven and which made its incorporation into the Liberal Alliance as well as its participation in the parliamentary political game inevitable. One of these motivations was ideological: the parties’ anticonservatism and anticlericalism. The other was practical: the necessity to “defend” their congressional seats, which forced them to find allies in the process of certifying the elections by the parliament. At the same time both motives came from the reformist character of the PD, its’ self-identification as the plebian side of liberalism (more resolute and consequent) and from its projectto democratically reform the oligarchic state