From this point onwards both parties would lose support in opinion polls and in successive regional and local elections.

[1][2] Voting was on the basis of universal suffrage, which comprised all nationals and resident non-national European citizens over 18 years of age and in full enjoyment of their political rights.

[7] The use of the electoral method resulted in an effective threshold based on the district magnitude and the distribution of votes among candidacies.

In order to be entitled to run, parties, federations, coalitions and groupings of electors needed to secure the signature of at least 15,000 registered electors; this requirement could be lifted and replaced through the signature of at least 50 elected officials—deputies, senators, MEPs or members from the legislative assemblies of autonomous communities or from local city councils.

However, a traffic accident in Badajoz the previous night resulting in the deaths of five people—one adult and four children—and 12 injured forced the suspension of the start of the campaign in Extremadura.

[32] On Monday 12 May, Isabel Carrasco, president of the provincial government of Leon and member of the PP, was shot dead in the street.

The highest percentage figure in each polling survey is displayed with its background shaded in the leading party's colour.

The table below lists opinion polling on the victory preferences for each party in the event of a European Parliament election taking place.

The table below lists opinion polling on the perceived likelihood of victory for each party in the event of a European Parliament election taking place.

[49] The People's Party (PP) came out on top in most autonomous communities except in Andalusia, Asturias and Extremadura, where the PSOE won; the Basque Country, where the PNV prevailed; and Catalonia, where ERC scored first place for the first time in 80 years.

Also, except for the autonomous cities of Ceuta and Melilla, it didn't surpass the 40% mark in any region, not even its strongholds of Galicia (where it polled a mere 35%), Castile and León or Castile-La Mancha (38% in both of them).

[62][63] One week after the election, Spanish King Juan Carlos I announced his intention to abdicate in favour of his son, Felipe.

[67][68] PP, PSOE, UPyD, Canarian Coalition (CC), Asturias Forum (FAC) and the Navarrese People's Union (UPN) all pledged their support to the law's approval.

[69] Attention then turned to the PSOE leader Alfredo Pérez Rubalcaba as rumours spread about him not resigning right away the day after the election to keep controlling the party so as to ensure the affirmative vote of its parliamentary group on the law.