The Unión Cívica Radical, the Radical Party, played a key role in pressuring the conservative elite into reform measures in 1912. Four years later, when the party won control of the presidency, a different era began in Argentina politics. Radicalism was the first major national political party in Argentina and among the earliest of the Latin American populist movements. Its central importance stemmed from its role as an agent of political integration, pursuing the broad objectives established by the reformers of 1912. In view of its later relationship with the urban middle class, it is important to see, however, that the party began in the 1890s as a minority splinter group from within the elite. Only later, after the turn of the century, did it develop its populist features when it evolved into a coalition movement between the elite sector and important segments of the middle classes. In the twenty-five years between 1891 and 1916 there were four major stages in the party's development: 1891–6, 1896–1905, 1905–12 and 1912–16. Its growth may be traced during these different periods from a number of separate perspectives: the party's composition and the extent of its popular support, and secondly its organisational features and regional connections.

The origins of Radicalism

During the first period up to 1896, the party was led by Leandro N. Alem. This coincided with the rebellions of the 1890s when a succession of attempts were made to overthrow the national government.