The 1987 Madrilenian regional election was held on Wednesday, 10 June 1987, to elect the 2nd Assembly of the Autonomous Community of Madrid. All 96 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, as well as the 1987 European Parliament election. The Spanish Socialist Workers' Party (PSOE) under Joaquín Leguina lost its overall majority in the Assembly, but remained the largest party. The most notable election result was the Democratic and Social Centre (CDS) breakthrough, emerging as the third largest party at the expense of all other parties in the regional parliament. The People's Alliance (AP) of newly elected AP Madrid leader Alberto Ruiz-Gallardón remained static, maintaining its position as the second largest party, while United Left (IU), a coalition of the Communist Party of Spain and other left-wing political forces, slipped to fourth place. In the aftermath of the election, the CDS chose to abstain in the investiture voting in order to allow the PSOE to continue to govern in minority. 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 President of the Community. 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. The electoral law provided that parties, federations, coalitions and groupings of electors were allowed to present lists of candidates. However, groupings of electors were required to secure the signature of at least 0.5 percent of the electors registered in the Community of Madrid. Electors were barred from signing for more than one list of candidates. Concurrently, parties and federations intending to enter in coalition to take part jointly at an election were required to inform the relevant Electoral Commission within ten