The Dominican Republic is a representative democracy in which all citizens may vote once they reach 18 years of age, or even earlier if they are married. The country's 1966 Constitution divides power among three branches: legislative, judicial, and executive. This similarity to the U.S. Constitution is no accident. After years of dictatorship under Rafael Trujillo, the country was in the midst of civil war when the United States invaded in 1965. The invasion was ostensibly to protect American citizens, but was also meant to curb the growing influence of leftist rebels and prevent their success. After establishing an inter-American peacekeeping force, the United States assisted the Dominicans in the formation of a new government. Following the U.S. model, legislative action is conducted by a bicameral National Congress, which consists of the Senate and the Chamber of Deputies, whose members face election every four years. The Senate's 30 members each represent a province while the chamber's 120 deputies are apportioned by population. Executive power is vested in the president who is elected to a four-year term. The president has the authority to appoint provincial governors and to remove them as well. He is also commander-in-chief of the armed forces although military commanders have also wielded great power as well.
There are four major political parties in the Dominican Republic: the Dominican Liberation Party (PLD), led by Leonel Fernández; the Social Christian Reformist Party (PRSC) of former president Joaquin Balaguer; the Dominican Revolutionary Party (PRD), the party of President Mejía, led by Hatuey De Camps; and a smaller party called the Democratic Union (UD). As in the United States, the party of the president does not necessarily enjoy a majority in the National Congress. Following the May 2002 elections, the president's PRD had 29 seats in the Senate and 73 in the Chamber of Deputies.