It would be the first time that the elections for two of the Spanish "historical regions"—namely, those comprising Andalusia, Catalonia, Galicia and the Basque Country itself—were held simultaneously.

[6][7][8] In response, the abertzale left asked their voters to cast invalid ballots, both in protest to the court rulings and seeking to prevent tactical voting in favour of either Lehendakari Juan José Ibarretxe's Basque Nationalist Party (PNV) or Eusko Alkartasuna (EA).

[9] The election resulted in an upset, as Basque nationalist parties lost their parliamentary majority for the first time in 30 years,[10][11][12] paving the way for a non-PNV led government.

Meanwhile, PNV's previous coalition partners, Eusko Alkartasuna (EA) and Ezker Batua (EB), suffered a harsh electoral downturn with both their leaders losing their seats and resigning in the aftermath of the election.

[19] Voting for the Parliament was on the basis of universal suffrage, which comprised all nationals over 18 years of age, registered in the Basque Country and in full enjoyment of their political rights.

The 75 members of the Basque Parliament 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.

[19][20] The lehendakari had the prerogative to dissolve the Basque Parliament at any given time and call a snap election, provided that no motion of no confidence was in process.

[21] Lehendakari Ibarretxe had been scheduled to announce a snap election for autumn 2008 following his expected failure in holding a proposed referendum on the Basque Country's political status for 25 October 2008, to be averted by the Spanish government.

[34] Later into the legislature on 28 September 2007, Ibarretxe attempted to revive his statute reform plan by announcing a new "right to decide roadmap" which provided for a referendum on the proposal being held by 25 October 2008, whether it was in agreement with the Spanish government or without it.

[46] Concurrently, and in application of the 2002 Law of Political Parties—which allowed the outlawing of parties "whose activity violates democratic principles, particularly when it seeks to deteriorate or destroy the regime of freedoms or prevent or eliminate the democratic system by promoting, justifying or exculpating attacks on the life or integrity of people, legitimizing violence as a method to achieve political objectives or politically supporting the action of terrorist organizations to achieve their purposes of subverting the constitutional order"[47][48][49]—the Supreme Court and the Constitutional Court barred several parties from contesting elections because of their reported ties to ETA and the outlawed Batasuna party;[8] namely, the Communist Party of the Basque Homelands (PCTV/EHAK),[4][50] Basque Nationalist Action (ANV),[3][51] several groupings created specifically to contest the 2007 local elections (such as Abertzale Sozialisten Batasuna and Abertzale Sozialistak)[52][53][54] or the 2009 regional election (Demokrazia Hiru Milioi and Askatasuna).

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

After Demokrazia Hiru Milioi (D3M) and Askatasuna ("Freedom") were outlawed in February 2009,[6][7] Basque separatists were asked to cast their vote for D3M, whose ballots would be counted as invalid.

[76][77] As the PNV–EA–EB alliance—in government since 2001—was no longer workable,[78] the PNV attempted to figure out a coalition agreement with the PSE to remain in power,[79] mirroring the historical collaboration that the two parties had maintained from 1986 to 1998,[80][81] and hinting at withdrawing PNV's support to Prime Minister José Luis Rodríguez Zapatero's government in the Cortes Generales if the Spanish Socialist Workers' Party (PSOE) did not back their plan.

[97] López was elected as new lehendakari on a 39–35 vote in the investiture session held on 5 May 2009,[98] garnering the additional support of the sole legislator from Union, Progress and Democracy (UPyD),[99] and was sworn in two days later.