But many questions remain unanswered. Seven of the principal suspects blew themselves up in an apartment building in Leganes on April 3, as police laid siege outside. The judge conducting the overall investigation, Juan del Olmo, has not publicized any preliminary findings.
The current Socialist government has insisted the attacks were not intended to change the outcome of the election and has accused opponents of using such inferences to question its victory. "There is no evidence to indicate the intention of the terrorists was really to change the Spanish government," said a Socialist Party spokesman, who spoke only on condition of anonymity. "You can't go looking for motives behind terrorist activity. Terrorists always act when and how they can. Spaniards went to the polls on March 14 and voted in an adult, free way and decided to vote against the PP government" and for the Socialist government, he said.
A closed-circuit television image shows people fleeing moments after a bomb exploded at a Madrid train station in March.
But the theory of a an electoral motive gained currency recently when the daily newspaper El Mundo published what it said was a transcript of a tape-recorded telephone conversation between Ahmed and an alleged accomplice shortly after the election. The recording was reportedly made on June 5 by Digos, the Italian anti-terrorism police force, as part of a 1 1/2-month surveillance operation that used listening devices on his home telephone line, according to European investigative sources.
In the conversation, Ahmed said that he was "immensely happy that the government of the dog Aznar has fallen."
According to the transcripts, he praised Zapatero for starting a new dialogue with Arabs and with Morocco. Referring to Aznar's cooperation with President Bush, Ahmed said, "Whoever follows the dog will only have an earthquake, and Madrid is proof of that. The people, the nation, are against supporting the Americans and the Iraq war."
El Mundo did not say how it obtained the transcripts. A spokesman for the Milan prosecutor's office declined comment on the newspaper report.
Some analysts, particularly government critics, say the tape lends new credence to the view that the attackers deliberately set out to influence the Spanish election, and succeeded.
"The more I think about it, the more I think that was absolutely the case," said Gustavo de Aristegui, a member of Spain's parliament and foreign affairs spokesman for the Popular Party. "If they had done it on the 10th, the government would have had time to react. If they had done it on the 12th, people would not have had time to change their minds and think it was Islamic extremists and not ETA." He added, "If they had chosen any other day of the week, the result would have been different."
Garcia-Abadillo of El Mundo offered a similar view. "It was the first time the Islamic fundamentalists had an attack that had a very clear end," he said. He recounted the sequence of events, including the discovery of the van with the Arabic language cassette, and the videotape with the claim of responsibility, on the eve of the election. "It's not a coincidence," he said.
Garcia-Abadillo and others interviewed here pointed to one other intriguing piece of evidence. On Saturday, March 13, police arrested a key suspect, Jamal Zougam, who ran a telephone shop and is believed to have supplied the cell phones used to trigger the explosives.
Zougam was kept secluded in custody for five days, as is allowed under Spain's anti-terrorism laws. When he was brought out of seclusion, on the evening of Thursday, March 18, to be examined by a doctor, his first words were: "Who won the election?"
"The mastermind of the attacks had a very deep awareness of the political landscape inside Spain," Garcia-Abadillo said. "He knew it would make Aznar's party lose the election."
Ahmed was heard in one intercepted call referring to the March 11 attacks as "my project." But investigators believe he is subordinate to another al Qaeda operative, Amer Azizi, also known as Othman Andalusi. He is believed to have trained in camps in Bosnia and to have met in Turkey prior to the attacks with a Moroccan Spanish ringleader in the attack, Sarhane Ben Abdelmajid Fakhet, known as "the Tunisian."
Focus on Al Qaeda Aide
Spanish authorities are now focusing on a senior al Qaeda operative close to Osama bin Laden who they believe was the overall plot organizer, a Syrian-born former journalist named Abu Musab Suri. He had married a Spanish woman and took Spanish nationality in the mid-1990s.