Chile's government is a representative democratic republic, whereby the President of Chile is both head of state and head of government, and of a formal multi-party system that in practice behaves like a two-party one, due to binomialism. Executive power is exercised by the government. Legislative power is vested in both the government and the two chambers of the National Congress. The Judiciary is independent of the executive and the legislature of Chile. The Constitution of Chile was approved in a national plebiscite in September 1980, under the military government of dictator Augusto Pinochet.