After the consolidation of the institutions of the Second Republic, Costa Rica entered a stage of political maturity characterized by the predominance of two major forces: the Partido Liberación Nacional (PLN) and the Partido Unidad Social Cristiana (PUSC). This period, which covered much of the final decades of the 20th century, gave the country enviable stability within the region, although it also sowed the seeds of its own transformation.

The Era of Bipartisanship and Consensus

Between 1986 and 2000, the electoral system functioned almost mechanically. The alternation in power between the PLN and the PUSC allowed continuity in the development model. During these years, Costa Rica not only strengthened its internal democracy but also projected its leadership internationally. A fundamental milestone was the signing of the Esquipulas II Peace Plan under the leadership of President Óscar Arias Sánchez, which sought democratization and the end of armed conflicts in Central America, reaffirming Costa Rica’s role as the civilist reference of the region.

The “PLUSC” and Citizen Discontent

Over time, the programmatic closeness between the two majority parties led a sector of the population to coin the term “PLUSC” to refer to what they perceived as a single, undifferentiated power bloc. Academic sources indicate that this period began to show signs of exhaustion due to:

Corruption scandals: Cases involving high-level figures affected trust in traditional institutions.
Electoral dealignment: A growing number of citizens stopped identifying emotionally with party colors (the “party-line vote”).
Increase in abstentionism: Participation, which historically exceeded 80%, began to decline, reflecting a disconnect between political supply and social demands.

2002: The Break in the System

The 2002 elections marked a point of no return. The emergence of the Partido Acción Ciudadana (PAC), led by Ottón Solís, broke the bipartisan monopoly and forced, for the first time in modern history under the 1949 Constitution, a second electoral round. This event transformed the system from a “perfect bipartisanship” to one of limited pluralism, where majorities in the Legislative Assembly became more difficult to achieve, requiring greater capacity for negotiation and coalition-building.

Toward Multipartism (2014–2018)

Fragmentation deepened in the following decade. In 2014, the PAC reached the presidency, ending decades of PLN-PUSC alternation. By 2018, the political landscape became even more complex with the entry of religious and values-based issues into the agenda, resulting in a significantly higher Effective Number of Parties (ENP). Costa Rican democracy shifted from being a predictable system to a vibrant, diverse, and at times polarized one, reflecting a society that is more critical and less willing to hand “blank checks” to its leaders.

Sources consulted:

• Sistema de partidos en Costa Rica en el periodo 1986-2018: del bipartidismo al multipartidismo, Carlos Cuitiño Burone.
• La paz en Centroamérica, 1987-1990. El Plan Arias desde adentro, Cristina Eguizábal Mendoza.
• Transición política en Costa Rica y el Partido Acción Ciudadana, Carlos Alvarado Quesada (Nuevo Mundo Mundos Nuevos).
• Crisis política y bipartidismo en Costa Rica: Apuntes sobre hechos recientes, Dialnet.
• ¿Cómo hemos cambiado? Progresos y desmejoras en la democracia costarricense, Informe Estado de la Nación.