The ruling Spanish Socialist Workers' Party (PSOE), on the other hand, fell to second place with 38.8% of the votes after a cycle of electoral victories starting in 2004.

The Coalition for Europe (CEU), the alliance of regionalist and peripheral nationalist parties that came to succeed the late Galeusca–Peoples of Europe coalition, remained in third place with 5.1% of the votes, whereas United Left (IU)—which ran under The Left banner—saw its worst showing in a nationwide election up to that point, barely surpassing 3.7% of the share.

After the Treaty of Lisbon came into force on 1 December 2011, Spain's delegation was increased to 54, granting additional seats to the PSOE (two) and to PP and CEU (one each) according to their June 2009 election results.

[a] 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.

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.