The Colorado and National parties and, to a lesser extent, the Broad Front coalition, were the three major political entities in 1990. Until the 1971 elections, the Colorado and National parties together accounted for 90 percent of the votes cast the remaining 10 percent of the votes were divided among vÍÍÍÍarious small parties. Some of the minor parties have followed the lead of the major parties and sought to enhance their electoral chances through coalitions, such as the Broad Front. The traditional two-party system was threatened for the first time by the Broad Front's victory in the Montevideo municipal elections in 1989, its first win on the national level.

As previously noted, a system of coparticipation (coparticipación) in the government between the ruling party and the principal opposition has characterized Uruguayan politics since 1872. According to Weinstein, this term best described Uruguay's unique political process and was still widely used among Uruguayans in the 1980s. Coparticipation meant that the two traditional parties and their members were entitled to divide and share the governing of the country. Indeed, in order to govern, the majority party had to make alliances with other parties because being the majority party in a proportional representation system did not necessarily mean that it had a simple majority in the General Assembly. For example, the Colorado Party almost always governed in alliance with a section of the National Party. During the first years of the Sanguinetti administration, the National Party refrained from systematic opposition, thereby helping to ease the legislative passage of government policies. The Colorado Party was expected to do the same for the Lacalle government. Sharing political power also has been determined by the principle of parity (paridad), meaning that the losing party's participation in the government was based on the relative electoral strength of the two parties.

Each party permitted internal ideological divisions because each party could run multiple presidential candidates and its own slate of legislative nominees. Factions, or sub-lemas, fielded different lists of candidates for general elections. Voters expressed a preference for a list rather than an individual candidate, and they voted for a party. The winning list of the party that received the most votes won the presidency and a percentage of the seats in the Senate and the Chamber of Representatives corresponding to the percentage of votes that the party as a whole received. National and departmental elections were held simultaneously every five years. Campaigns were funded in part by government subsidies given to the parties and factions in accordance with their voting strength in the previous election.

Data as of December 1990