Its historical roots are in Calderonism, i.e. the movement of supporters of Rafael Ángel Calderón Guardia, who was the country's president in the 1940s.

Thus, Rafael Ángel Calderón Fournier the Coalition's candidate in the 1982 general election suffered a debacle gaining only 33% of the votes and PLN obtaining a landslide victory.

After a series of complex sessions, Democratic Renovation's National Assembly finally agree by a slight majority to merge and PUSC was born and Costa Rica passed from a dominant-party system into a two-party system with PLN and PUSC as main political forces.

[3] In the 1990 election, following the aforementioned primary, Calderón won over PLN's candidate Carlos Manuel Castillo.

[3] The next primary was held on June 10, 2001 between then deputy and TV personality Dr. Abel Pacheco de la Espriella and former minister Rodolfo Mendez Mata.

They were accused of receiving money in exchange for guaranteeing very profitable contracts between private companies Alcatel and Fischel with State's corporations.

Fishman was the first Jewish presidential candidate in Costa Rica's history and gained 5% of the votes keeping the 5 seats.

[3] In 2013 Calderón suggested Dr. Rodolfo Hernández, then director of Costa Rica's Children's Hospital, as 2014's presidential nominee.

Yet Hernández resigns as candidate on October 3, 2013 alleging constant backstabbing and treacheries from PUSC's authorities, so the party's nomination was taken by Rodolfo Piza.