In 1955, there was a popular uprising led by Mexican socialist and leftist revolutionaries against the presidency of Umberto Ruiz. Although Ruiz was a member of the historically left-wing Institutional Revolutionary Party (PRI) (which had operated de facto one-party rule since the end of the Revolution), he and his predecessors since the conclusion of World War II, shifted the policies of the party towards the right, in support of the international business community and social conservatives, which was seen as a betrayal to the principles and ideals of the Revolution of 1910. Ruiz repressed labor strikes and political demonstrations prolifically during his administration, and held extensive ties with foreign companies centered in the Yucatán, which included agriculture and mining companies