Legislative power is vested in both the government and the National Assembly. The Judiciary is independent of the executive and the legislature.
São Tomé has functioned under a multiparty system since 1990. Following the promulgation of a new constitution in 1990, São Tomé and Príncipe held multiparty elections for the first time since independence.
Shortly after the constitution took effect, the National Assembly formally legalized opposition parties. Independent candidates also were permitted to participate in the January 1991 legislative elections.
The president of the republic is elected to a five-year term by direct universal suffrage and a secret ballot, and may hold up to two consecutive terms. Candidates are chosen at their party's national conference (or individuals may run independently). A presidential candidate must obtain an outright majority of the popular vote in either a first or second round of voting in order to be elected president.
The prime minister is named by the president but must be ratified by the majority party and thus normally comes from a list of its choosing. The prime minister, in turn, names the 14 members of the cabinet.
The National Assembly (Assembleia Nacional) has 55 members, elected for a four-year term in seven multi-member constituencies by proportional representation. It is the supreme organ of the state and the highest legislative body, and meets semiannually.
Justice is administered at the highest level by the Supreme Court. Formerly responsible to the National Assembly, the judiciary is now independent under the new constitution.