The constitution states that the people exercise political power through universal, equal, direct, secret, and periodic elections. All citizens over the age of eighteen have the right to vote, and those over the age of twenty-one have the right to hold public office, under conditions of equality and freedom. Portuguese citizens are obliged to register to vote, but voting itself is voluntary. Freedom of association is guaranteed and is defined to include the right to establish or join political parties and "through them to work democratically to give form to the will of the people and to organize political power."

Elections for the president's term of five years in Portugal's semi-presidential system are by popular vote. If a candidate fails to receive an absolute majority on the first ballot, a runoff election between the two leading candidates is to be held within two weeks.

Elections for the four-year legislative terms of the Assembly of the Republic are by proportional representation in each constituency. Portugal uses the d'Hondt method of proportional representation, which is based on the highest average method and favors large parties by awarding them a greater percentage of assembly seats than the percentage of votes they won. Small parties are protected in that there is no minimum percentage of votes they must receive to gain a seat in the assembly. Nonetheless, unless these parties were members of a coalition, they rarely won a seat in the assembly. The d'Hondt method was adopted because it leads to stronger, more stable governments in countries that are deeply divided and have multiple parties.

Municipal elections, which served as a barometer of public opinion on the national government, are held every four years. In contrast to national elections, this schedule was maintained because local governments did not fall. The national parties participated in these elections.

Data as of January 1993