THE ELECTION: Spain's worst terror attack immediately cast a pall over Sunday's general election, with political parties declaring that campaigning would come to an abrupt halt as the country mourned.
"The campaign is over," said Mr Mariano Rajoy, who succeeds the Prime Minister, Mr José Maria Aznar, as candidate for the ruling rightwing People's Party.
Sunday's vote will be carried out with the country in a state of profound shock, mourning and anger for the huge loss of life and hundreds of injuries provoked by the Madrid train bombs. It was unclear how the attack might sway voters, but it seemed likely to play towards the ruling People's Party, which has made the fight against Eta one of its main concerns over the past eight years.
The People's Party was already some four points ahead of the opposition Socialists in polls last weekend, but looked set to lose its absolute majority, which would force Mr Rajoy to seek allies in small regional parties.
A failed attempt by Eta in 1995 to assassinate Mr Aznar, whose "no negotiating" stance has won widespread support in Spain, was considered one of the factors that helped him win elections the following year.
In fact, Eta had already played a significant role in the election campaign, with the People's Party basing much of its strategy on the successes it has had against the organisation in recent years and attacking any sign of weakness among its opponents.
The Socialist opposition, led by Mr José Luis Rodriguez Zapatero, had been attacked, for example, for an alliance it has in the Catalan regional government with a non-violent separatist party, the Catalan Republican Left, that is known to have had talks with Eta.
When the leader of Catalan Republican Left, Mr Josep Luis Carod Rovira, was found to have met Eta in January this year, and Eta later called a ceasefire that covered only Catalonia, the People's Party accused him of directing the group to carry out attacks in other parts of Spain.
When a van carrying half a tonne of explosives was captured by police two weeks ago as it headed towards the Spanish capital, the Interior Minister, Mr Angel Acebes, said Mr Carod Rovira "must be very happy" that the separatists were targeting Madrid.
Similarly bitter comments could be heard on the streets of Madrid after yesterday's blasts.
The People's Party has continually asked the Socialists to explain why they have not kicked Mr Carod Rovira out of the coalition that they lead in Catalonia.
Debate over Eta has partially obscured an underlying, but equally important, debate over what to do with further demands for autonomy coming from moderate, non-violent nationalists in the Basque country and in Catalonia.
While both the People's Party and the Socialists have rejected attempts by the nationalists in the Basque country to declare themselves a "free associate" of Spain, the Socialists have said they would sit down and talk with the Catalans about their more moderate demands.
The People's Party, on the other hand, has rejected giving more powers to either region, claiming both already have extensive self-government and calling the Basque plan "treason".
There were warnings from some politicians against any attempts to use yesterday's attacks for campaign purposes. Both Mr Rajoy and Mr Zapatero said yesterday that it was a moment for unity between the main political parties.
"What the killers want us to do is to lose our calm and create confrontations between us. Let's do the opposite," Mr Zapatero said.
"It is a time for unifying forces," Mr Rajoy said.