By Steve Kingstone
BBC News, Madrid
The governing Basque Nationalist Party will not give up power lightly
Rarely do regional elections set pulse-rates racing, but Sunday's votes in Galicia and the Basque Country were genuinely exciting, and have produced political shifts which may have nationwide repercussions.
In the case of the Basque vote, history has been made.
For the first time since Spain's transition to democracy following the death of General Franco in 1975, non-nationalist parties have been elected the majority force in the Basque regional parliament.
Together, the Basque Socialist Party (PSE), the conservative People's Party (PP) and the smaller Union, Progress and Democracy Party (UPD) boast 38 parliamentary seats; one more than the governing Basque Nationalist Party (PNV) and its potential allies.
The question is whether these "Spanish" parties now join together in a formal governing alliance, to exclude the nationalists from power for the first time in three decades?
Certainly, the Socialists' leader, Patxi Lopez, sounds like a man who wants to govern.
"I feel legitimised to lead the change," he announced after final results were confirmed, having argued during the campaign that Basques needed practical solutions to the economic crisis, rather than grand plans for sovereignty, as proposed by the nationalists.
But the PNV will not give up power lightly.
In terms of seats and share of the vote, the party remains the largest political force in the parliament, and its failure to secure an absolute majority was principally down to a disappointing performance by smaller coalition partners.
Mr Ibarretxe looked and sounded deeply emotional after the final results
"We have won the election, it is OK to celebrate," was the upbeat message to supporters by the PNV's Juan Jose Ibarretxe, who has been the lehendakari - president of the Basque regional government - for the past decade.
But Mr Ibarretxe looked and sounded deeply emotional, as if trying to reassure himself that he still had a political future.
It is by no means inconceivable that the nationalists will offer to share power with the Socialists in a grand coalition.
The two parties already work in partnership in the Spanish parliament in Madrid, where Prime Minister Jose Luis Rodriguez Zapatero and his Socialist Party (PSOE) relies on PNV votes.
But Mr Zapatero has promised not to interfere in negotiations towards a Basque coalition; and to say the least, it is difficult to imagine Messrs Lopez and Ibarretxe sitting around the same cabinet table.
Prime Minister Zapatero's PSE ally Patxi Lopez could soon be in power
If the Socialists do make history and lead the new administration, what effect might it have on the strategy of the Basque separatist movement, Eta?
Before polling, the gunmen branded the election "anti-democratic", on the grounds that the Spanish Supreme Court had banned two radical separatist parties from taking part.
The group portrayed the court ruling as a plot by the Spanish authorities to manufacture a Socialist victory.
If the moderate PNV is now forced out of government, Eta will claim to be a more effective voice for the Basque cause.
People's Party resurgent
In north-western Spain, the coastal region of Galicia produced a result which may offer clearer pointers to future nationwide trends.
Having governed for four years in coalition with Galician nationalists, the Socialists were defeated by a resurgent People's Party, which regained control of a region which was historically a conservative stronghold.
People's Party leader Mariano Rajoy proclaimed a brilliant electoral victory
Needing 38 seats for an absolute parliamentary majority, the PP secured 39.
The result is a personal triumph for the nationwide conservative leader, Mariano Rajoy, a Galician who had committed considerable time and resources to securing victory in his home region.
Having lost two consecutive general elections to the Socialists, Mr Rajoy had seen his own authority questioned, while in recent weeks the party had been dogged by in-fighting and persistent corruption allegations.
Outside his party headquarters in Madrid, the usually reserved conservative leader was feted by young supporters.
He proclaimed a "quite brilliant electoral victory… in very difficult circumstances".
For now at least, the win puts to bed any notion that Mr Rajoy will fall victim to an internal coup.
As for the governing Socialist Party, the manner of its defeat in Galicia is especially worrying.
For months, opinion polls had suggested its coalition would prove immune to the conservative attack; but as the dire economic news piled up, so the poll lead shrank.
With Spain now deep in recession, and saddled with the EU's highest unemployment rate, the Socialists will look ahead to June's European Parliament elections with some trepidation.