The 1991 Madrilenian regional election was held on Sunday, 26 May 1991, to elect the 3rd Assembly of the Autonomous Community of Madrid. All 101 seats in the Assembly were up for election. The election was held simultaneously with regional elections in twelve other autonomous communities and local elections all throughout Spain. The election saw the electoral collapse of the Democratic and Social Centre (CDS), which fell below the 5% threshold and lost all their 17 seats. Alberto Ruiz-Gallardón's People's Party (PP) emerged as the largest party in the community for the first time, but was unable to form a government due to the lack of allies as a result of CDS expulsion from the Assembly. Consequently, Joaquín Leguina from the Spanish Socialist Workers' Party (PSOE) was re-elected President for a third term in office thanks to the support of United Left (IU). Overview Electoral system The Assembly of Madrid was the devolved, unicameral legislature of the autonomous community of Madrid, having legislative power in regional matters as defined by the Spanish Constitution and the Madrilenian Statute of Autonomy, as well as the ability to vote confidence in or withdraw it from a regional president. Voting for the Assembly was on the basis of universal suffrage, which comprised all nationals over 18 years of age, registered in the Community of Madrid and in full enjoyment of their political rights. All members of the Assembly of Madrid were elected using the D'Hondt method and a closed list proportional representation, with an electoral threshold of five percent of valid votes—which included blank ballots—being applied regionally. The Assembly was entitled to one member per each 50,000 inhabitants or fraction greater than 25,000. Election date The term of the Assembly of Madrid expired four years after the date of its previous election. Legal amendments earlier in 1991 established that elections to the Assembly were to be fixed for the fourth Sunday of May every four years. The previous election was held on 10 June 1987, setting the election date for the Assembly on Sunday, 26 May 1991. After legal amendments in 1990, the president was granted the prerogative to dissolve the Assembly of Madrid and call a snap election, provided that no motion of no confidence was in process and that dissolution did not occur before one year had elapsed since the previous one. In the event of an investiture process failing to elect