Two traditional parties, the Conservatives and the Liberals, have dominated Colombian formal politics since the middle of the nineteenth century. From 1886 until 1930, the Conservatives ruled, but in that year a split in the Conservative ranks brought the Liberals to power, with the election of Enrique Olaya Herrera. Then, in 1934 the Liberals won again with the candidacy of Alfonso López Pumarejo, who launched a series of important reforms. These included encouragement of the organized labor movement, tax reforms, and strong State support for economic development.
However, although the Conservatives under the leadership of the reactionary Laureano Gómez largely refused to participate in elections between 1934 and 1946, the reform program of Alfonso López Pumarejo aroused considerable opposition within the Liberal ranks. As a consequence, the "moderate" Liberal Eduardo Santos, publisher of the country's most important newspaper, El Tiempo, was elected in 1938, and he restrained the Liberals' reforming zeal.
Alfonso López Pumarejo was reelected in 1942. However, faced with economic problems generated by World War II, considerable corruption within the regime, and growing disillusionment on the part of organized workers and other popular elements, López resigned early in 1945, and his place was taken by Alberto Lleras Camargo, his vice president.
At the end of Lleras Camargo's term in 1946, the Conservatives returned to the hustings. As a consequence of a split in the Liberal Party between the "official"