Carl Lindhagen was one of Sweden’s most well-known politicians at the beginning ofthe 20th century. He entered parliament as a Liberal in 1897 but joined the Social Democrats in 1909. In 1917 he became a key figure in forming the Left Socialist party,which became the Swedish Communist Party in 1921 – although it expelled him in that moment. He returned to the Social Democrats in 1923. During those years, Sweden gradually moved towards universal suffrage, including most men in 1909 and women in 1921. As an MP, Lindhagen was a central actor in debates concerning democracy, combining the roles of the visionary political thinker and the hands-on political practitioner, and doing so in ways that would spark both enthusiasm and controversy among his contemporaries. This dissertation examines how Lindhagen interpreted the transformation of politics 1896–1923, how he envisioned a future of “true” democracy and the steps he took to realize his ideals. In his perspective, the constitutional reforms of the 1910s and the 1920s only achieved “formal” democracy. From the early 1910s he preferred to label himself as a ”humanist”, seeing Liberalism and Socialism as temporary forces, contributing elements to a historical process approaching the universal values of “humanism”. In 1919 he also created a party transcending organization for “humanist politics”, gathering like-minded people among Left Socialists, Social Democrats, and Liberal leftists.This study concentrates on Lindhagen’s most active and influential years, finding its central sources in texts which he wrote, modified, used and reused, for many purposes within the parliament and in his party organizations, as well as in addressing a general public. Three chronological parts follow Lindhagen through his political affiliations, 1896–1909,1909–1917, and 1917–1923. The study shows a remarkable amount of continuity in Lindhagen’s attitudes and positions, although he elaborated them, as well as the language he used to express them, due to new experiences, situations, and political environments. This makes him a tellingly complex case in the historiography of Liberalism, Social Democracy, and Communism in Sweden. Adding to this telling complexity is also the way in which Lindhagen gradually focused more and more on political parties as a central political problem, stressing that a condition for “true democracy” was practical measures of democracy at alllevels in the political process, especially within the political parties which took theirmodern form during the era studied in the dissertation.