The PSOE under José Luis Rodríguez Zapatero benefitted from tactical voting against the PP and emerged as the most-voted party just 7 seats short of an overall majority.

Union, Progress and Democracy (UPyD), with 1 seat and slightly more than 300,000 votes, became the first nationwide party aside from PSOE, PP and IU entering in parliament in over two decades.

Zapatero was sworn in as Prime Minister of Spain for a second term in office in April 2008, just as the Spanish economy began showing signs of fatigue and economic slowdown after a decade of growth.

[1][2] 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.

[3][4] 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.

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.

[15][16] The Cortes Generales were officially dissolved on 15 January 2008 after the publication of the dissolution decree in the BOE, setting the election date for 9 March and scheduling for both chambers to reconvene on 1 April.

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, terrorism or other crimes against the state.

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.

[23][24] 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.

The second phase was done under the slogan "La Mirada Positiva" (The Positive outlook), emphasising the future government platform, and "Vota con todas tus fuerzas" (Vote with all of your strength), aiming to mobilize the indecisive or potentially abstaining voters.