Its strongholds have been the miners and industrial workers of Biscay, Guipúzcoa and Asturias, the landless labourers of Andalusia and Extremadura and, since the 1970s, the public officers across Spain.
It has had strong ties with the Unión General de Trabajadores trade union.
For decades, UGT membership was a requisite for PSOE membership.
During the ruling of PSOE in the 1980s, though, UGT protested the PSOE economic policy, even calling to a general strike (14-D) on 14 December of 1988.
During the dictatorship of Francisco Franco (1939-1975) the PSOE was illegal and it was persecuted. Many of their leaders and militants were assassinated, imprisoned or they exiled to France, the United States, or Mexico. In the first democratic elections (1977), it arose as the second party of Spain, with 30% of the votes. In 1979 it obtained similars results. From 1974, its general secretary was Felipe González, who in a congress at Suresnes (France), moved the party away from its Marxist and socialist path, turning the PSOE into a social-democratic party, similar to those of the rest of western Europe. To this end, he banned the Marxist wing, directed by the Trotskyist newspaper New Clarity, similar to the British Socialist Appeal (former Militant).
These movements were encouraged by the European social democracy; German SPD granted money to PSOE.
In 1982, the PSOE won an historic electoral victory, with more than 10,000,000 votes (48%). Felipe González became Prime minister, a position that he occupied from 1982 to 1996. In spite of its appearance as a leftist party, with a progressive program, the PSOE made a policy of social reforms combined with a liberal and capìtalist economic policy. In addition, it was favorable to the entrance of Spain in NATO (1986) and supported the United States in the Gulf War (1991). The PSOE won 1986, 1989 and 1993 elections.
An economic crisis, scandals of corruption and state terrorism against the Basque violent separatist group ETA eroded the popularity of Felipe González, and in 1996, the PSOE lost the elections to the conservative Partido Popular ("Popular Party") (PP). Between 1996 and 2001 the PSOE weathered a crisis, suffering a hard defeat in 2000 (34.7%), after agreeing with Izquierda Unida ("United Left") (IU).
It still has remained as the ruling party in the autonomous communities of Andalusia, Extremadura, Castilla-La Mancha and Asturias. 13th November 2003 the PSOE won catalonian election, and has the autonomous government, Generalitat, with a pact with Esquerra Republicana de Catalunya (Republican Left of Catalonia, ERC, left-wing independentist) and Izquierda Unida (United Left, IU).
In 2001, a new general secretary, José Luis Rodríguez Zapatero, was elected, replacing Felipe González, and renewing the party. Later, the PSOE won the municipal elections of 2003.
Baron. The regional leaders. They can be very powerful, especially if they run an autonomous community. There have been conflicts between barons and the central directorate. Some barons are Pasqual Maragall (Catalonia), José Luis Ibarra (Extremadura), Chaves (Andalusia). (Enrique Barón was a PSOE minister for Industry, the surname is a coincidence). The term baron is more coloquial than official, representing the great power than these persons have in the party.
Compañero ("companion"). A term of address among Socialists, similar to the communist comrade. After the social-democratization, it is out of vogue and only used during campaigns or by the most leftist socialists.
Currents. There have been several internal groups within PSOE, based on personal or ideological affinities. Some of them have ended with separation from the PSOE. The failed trial of primary elections for PSOE candidates was an attempt to conciliate currents. Examples of currents are "Guerristas" (followers of Alfonso Guerra), "Renovadores" (renewers, right-wing of the Party) or Izquierda Socialista (Socialist Left).