The incumbent People's Party (PP) of Prime Minister José María Aznar secured an unpredicted absolute majority in the Congress of Deputies, obtaining 183 out of 350 seats and increasing its margin of victory with the opposition Spanish Socialist Workers' Party (PSOE) to 2.4 million votes.

Such an alliance was said to prompt tactical voting for the PP, which also benefited from economic growth, a moderate stance throughout the legislature and internal struggles within the opposition parties.

[3] Regional and peripheral nationalist parties improved their results, except for Convergence and Union (CiU)—which had been in electoral decline for a decade—and Herri Batasuna/Euskal Herritarrok (EH), which urged to boycott the election and called for their supporters to abstain in the Basque Country and Navarre.

The voters' turnout registered was one of the lowest in democratic Spain for Spanish election standards, with only 68.7% of the electorate casting a vote.

[6][7] Voting for the Cortes Generales was on the basis of universal suffrage, which comprised all nationals over 18 years of age and in full enjoyment of their political rights.

[8][9] For the Congress of Deputies, 348 seats were elected using the D'Hondt method and a closed list proportional representation, with an electoral threshold of three percent of valid votes—which included blank ballots—being applied in each constituency.

[18][19] The prime minister had the prerogative to propose the monarch to dissolve both chambers at any given time—either jointly or separately—and call a snap election, provided that no motion of no confidence was in process, no state of emergency was in force and that dissolution did not occur before one year had elapsed since the previous one.

[35][36] The Cortes Generales were officially dissolved on 18 January 2000 after the publication of the dissolution decree in the BOE, setting the election date for 12 March and scheduling for both chambers to reconvene on 5 April.

Anguita sought to prevent an electoral alliance between United Left–Galician Left (EU–EG) and the Socialists' Party of Galicia (PSdeG–PSOE) ahead of the 1997 Galician regional election,[67] a move which received criticism from Initiative for Catalonia (IC),[68][69] IU's sister party in Catalonia, with which disagreements over the coalition's political direction had been on the rise since the 1996 general election.

[74][75][76][77] The PDNI then sought electoral alliances with the PSOE,[78][79] which materialized ahead of the 1999 local, regional and European Parliament elections.

Spanish citizens of age and with the legal capacity to vote could run for election, provided that they were not sentenced to imprisonment by a final court's decision nor convicted by a judgement, even if not yet final, which imposed a penalty of forfeiture of eligibility or of specific disqualification or suspension from public office under specific offences: rebellion and terrorism when involving crimes against life, physical integrity or freedom of persons.

Other general causes of ineligibility were imposed on members of the Spanish royal family; the president and members of the Constitutional Court, the General Council of the Judiciary, the Supreme Court, the Council of State, the Court of Auditors and the Economic and Social Council; the Ombudsman; the State's Attorney General; high-ranking members—undersecretaries, secretaries-general, directors-general and chiefs of staff—of Spanish government departments, the Prime Minister's Office, government delegations, the Social Security and other government agencies; heads of diplomatic missions in foreign states or international organizations; judges and public prosecutors in active service; Armed Forces and police corps personnel in active service; members of electoral commissions; the chair of RTVE; the director of the Electoral Register Office; the governor and deputy governor of the Bank of Spain; the chairs of the Official Credit Institute and other official credit institutions; and members of the Nuclear Safety Council; as well as a number of territorial-level officers in the aforementioned government bodies and institutions being barred from running, during their tenure of office, in constituencies within the whole or part of their respective area of jurisdiction.

[91][92] Disqualification provisions for the Cortes Generales extended to any employee of a foreign state and to members of regional governments, as well as the impossibility of running simultaneously as candidate for both the Congress and Senate.

[111][112][113] Various attempts at forming a joint left-wing candidacy for the Senate in the Valencian Community were unsuccessful,[114][115][116] primarily due to disagreement over the label and format of such an alliance.

[117][118][119][120] Nationwide, an agreement was reached between the national leaderships of PSOE and United Left, under which both parties agreed to cooperate in the Senate elections for 27 constituencies: in those districts, and taking consideration of the Senate electoral system allowing up to three votes to each voter, the PSOE would field two candidates to one from IU, with the parties urging voters to cast their votes as if it were a joint list of three.