Over the weekend two Spanish regions, Galicia and the Basque country, are set to hold elections.
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The attack happened less than three weeks before regional elections in the Basque Country.
As a result, public spending per person in the Basque country is the highest in Spain.
The small nationalist parties from Catalonia, the Basque country and elsewhere hold the balance of power.
The Basque Country and Navarra collect their own taxes and pay the centre for services rendered.
There is another, far uglier, regional shadow over Spain: terrorism from the Basque Country.
Fortunately for those living here, the nationalist movement here is peaceful - unlike in the Basque country.
Mr Aznar particularly wants people who live in the Basque country but are not Basque nationalists to vote next month.
On borrowing costs for an independent Scotland, Prof Goodhart has to look to the Basque country to find any parallel, however imperfect.
On August 27th, the Basque regional police began to implement a legal order to shut down Batasuna offices throughout the Basque country.
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This might if their wildest dreams came true eventually include French bits of the Basque Country as well as the Spanish province of Navarre.
On October 21, both the Basque country and Galicia held regional elections.
Catalonia's nearby regions, the Basque country, and Galicia in the Northwest of Spain also have self-governance mandates under the Spanish Constitution of 1978.
Railways have been a chosen target of Eta, which opposes the construction of a high-speed line between Madrid and the Basque Country, our correspondent says.
He fears that the Spanish government is trying to roll back some of the hard-won powers of regions such as Catalonia and the Basque country.
Until the mood in the Basque country turned sour last December, he had managed to get along, though not warmly, with the mainstream (non-violent) Basque nationalists.
Basque peace could be a pay-off for Mr Zapatero's softly-softly approach to Spain's most enduring political problem: regional tensions in the Basque country and in Catalonia.
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In the Basque country, it is the regional administration that collects all the taxes and passes a chunk to the centre, not the other way round.
But Javier Rojo, leader of the Socialist Party in the Basque Country, blamed ETA for Monday's blast and called it "a horrendous terrorist attack, " Reuters said.
ETA's, which might help put some pep into a mooted all-party initiative to re-examine the constitutional status of the Basque country and the neighbouring part-Basque province of Navarre.
The fathers of the constitution fudged their definition of Spain's three most independent-minded regions the Basque Country, Catalonia and Galicia by calling them nationalities (ie, neither full-blooded nations nor mere regions).
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But the fly-half, who missed five kicks at goal in the Basque country, saw his effort fall short as Biarritz surged into the semi-finals for the first time since 2006.
Two key inspirations are what Donald describes as "the primitive, soulful way of cooking" over fire in Uruguay, and the grilling wizard Victor Arguinzoniz, of Asador Etxebarri, in the Basque Country.
Mr Aznar has little room for manoeuvre, short of giving Basques total independence and most people in the Basque country, probably including a slim majority of ethnic Basques, want to stay Spanish.
Conservatives, Socialists and even the communist-led United Left have welcomed the sentences, while Basque nationalists of all stripes, who win just under half the votes in the Basque country, have expressed varying degrees of condemnation.
So long as the tension does not become thorough-going violence, it seems likely that both sides the government in Madrid and Basque nationalists across the board in the Basque Country will wait until the elections in June before they consider changing tack again.
After 25 years of a democratic system, including a strong dose of devolution for the Basque country, the government in Madrid thinks it is time to stop feeling guilty for Spain's past under Franco and to get tough on those who undermine freedom.
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It sees the dispute as a purely bilateral matter between the two governments and conceding any form of self-determination for the people of Gibraltar would set an unwelcome precedent that might be exploited by the separatist movement in the Basque country of northern Spain.
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