The pact between UPN and the PP, two centre-right parties, came about for different reasons of coexistence. UPN was the second political force in Navarre after the Socialist Party of Navarre (PSN-PSOE), and according to the law (Article 29 of Law 13/1982 of August 10th (LORAFNA), which would subsequently be replaced by Law 1/2001 of March 26th), meant that in the autonomous-community elections, the government would be formed from the most voted-for list in the event that no candidate was endorsed in the successive votes held within two months of the first. In addition, the PP could see that the electoral results were not at all in their favour in this autonomous community. The pact brought mutual benefits from the outset. UPN became the most voted-for political force in Navarre in the autonomous elections in 1991, taking power for the first time, and apart from a period of little over a year where there was a tripartite government consisting of the PSN, Convergencia de Demócratas de Navarra (CDN) (and Eusko Alkartasuna (EA), it has remained in power ever since. In addition, the PP had a number of UPN MPs and senators in the National Parliament Houses at its disposal, which it would not have been able to achieve alone.
The background to the break-up can be traced to the result of the last autonomous-community elections held in Navarre (May 2007), in which PSN-PSOE had the possibility of forming a government together with Nafarroa Bai and Izquierda Unida de Navarra (IU/EBN). This possibility of a three-party pact, encouraged by the leadership of the PSN at an autonomous-community level, came into conflict with the preferences of the socialist party's national level leadership, who were unhappy with the idea of a governmental coalition with Nafarroa Bai, a party of the so-called Basque radical left. Finally, the PSN decided not to form a coalition government and opted for supporting, or rather, allowing, a minority UPN government. This situation obliged UPN to moderate its posture towards the socialists, and the general budget, presented by the PSOE, became the element that triggered the end of the pact.
Although both parties accused each other mutually of causing the break-up, the change in the political strategies of both forces was the main reason for the rupture. The pact was no good to the PP if it could not count on the loyalty of UPN's MPs and senators in the Spanish Houses of Parliament during voting on a law as crucial as the general budget; while UPN came to see that the relationship with the PP meant limiting its own policy in the Spanish Parliament and a free relationship with central government, which alternates between PSOE and the PP.
