Seven months after bombs exploded aboard morning commuter trains in Madrid, killing 191 people, the precise motives of the attackers remain unclear. But new evidence, including wiretap transcripts, has lent support to a theory that the strike was carefully timed to take place three days before a national election in hopes of influencing Spanish voters to reject a government that sent troops to Iraq.

Some analysts argue that the placement of important clues -- particularly a videotaped claim of responsibility by a masked Islamic militant discovered two days after the March 11 attacks -- was aimed at quickly establishing that the attacks were a reaction to the presence of Spanish troops in Iraq and generating a backlash against the ruling Popular Party.

The party had a comfortable advantage in opinion polls but lost the election on March 14. The new Socialist party government of Prime Minister Jose Luis Rodriguez Zapatero quickly kept a campaign pledge to withdraw Spain's 1,300-troop contingent from Iraq. It also set about improving relations with neighboring Morocco, after two years of tension under the government of the previous prime minister, Jose Maria Aznar.

Newly disclosed wiretaps of an alleged organizer of the bombings expressing glee that "the dog Aznar" had been put out of office have prompted some analysts here to conclude that the perpetrators sought to try to bring about specific reactions through the attacks.

The general consensus among U.S. counterterrorism officials is that the Madrid attacks were timed to influence the Spanish elections, according to several intelligence officials. At the same time, U.S. officials acknowledge that the evidence is circumstantial at best.

"It's really an analysis more than a proven fact," said one law enforcement official, who declined to be identified because the information is classified. "We certainly don't have any statement that that's why they did it or anything. But it's the timing of it, the outcome and the continued threats to countries involved in Iraq that leads to that being the leading hypothesis."

Some U.S. and Spanish officials have pointed to the Madrid bombings in arguing that an attack may be planned in the United States in an effort to sway American voters on Nov. 2. "It's a lesson for everybody because an attack like this changed the government," said Casimiro Garcia-Abadillo, a deputy editor of El Mundo newspaper and author of a new book, "11-M, La Venganza" ("March 11, The Revenge"). "It was a coup d'etat undercover."

The FBI is leading a massive campaign of interviews, arrests and other measures aimed at disrupting any potential terrorist plots before the Nov. 2 U.S. elections.

In July, Secretary of Homeland Security Tom Ridge said that "based on the attack in Madrid" and the interdiction of other intelligence "we know that they have the capability to succeed, and they hold the mistaken belief that their attacks will have an impact on America's resolve."

Experts also said they believed it was irrelevant whether the Madrid attacks were intended to sway the elections; they did, and that has apparently been noted by Osama bin Laden, the al Qaeda leader. In an audiotape released on April 15, a voice believed to be that of bin Laden praised the Madrid bombings and proposed a "reconciliation" with any country "that commits itself to not attacking Muslims or interfering in their affairs, including the U.S. conspiracy on the greater Muslim world." Otherwise, he warned, "the situation will expand and increase."

Immediately after the Madrid attacks, a claim of responsibility by an al Qaeda-linked group was e-mailed to the London-based Al-Quds al-Arabi newspaper. On the evening of March 11, a stolen van was discovered abandoned east of the Spanish capital in which police found a cassette tape of Koranic verses and blasting caps.

Two days after the blast, police were led to a garbage can outside a mosque that contained a videotape showing a masked man, now believed to be Rachid Oulad Akcha, a Moroccan immigrant, calling the attacks "a response to your collaboration with the criminal Bush and his allies."

People familiar with this fast-moving sequence of events say it suggests the attackers wanted to make certain that Spanish voters knew that Islamic radicals -- and not the Basque separatist group ETA -- were responsible when they went to the polls so they would punish the ruling party. The dispatch of troops to Iraq by Aznar was intensely unpopular in Spain, and any link between the attack and the Iraq mission was likely to rebound at the polls, many analysts said in the days after the bombings.

One purported planner of the plot, Rabei Osman Sayed Ahmed, known as "Mohamed the Egyptian," was arrested in Milan and remains in Italian custody, facing terrorism charges and possible extradition to Spain. Twenty other suspects are in custody.

Motive Disputed

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.

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 11/2-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.

Suri, also called Mustafa Setmarian Nasar, is thought to be 45 years old. European intelligence agencies have said that he was once the overall commander of al Qaeda training camps in Afghanistan and once headed al Qaeda's propaganda operation.

After the attacks of Sept. 11, 2001, investigators thought he was part of an al Qaeda faction that distanced itself from bin Laden's leadership. But more recently, European intelligence agencies have questioned that view and come to believe Suri may have traveled to Europe last year to activate some of the al Qaeda groups in Spain and elsewhere.

The investigations into the attacks, including one by a parliamentary commission that has often degenerated into partisan bickering, have also suggested that Spanish authorities, who for years have been focused on blocking Basque terror attacks, may have missed key chances to discover the March 11 plot.

Many of the key suspects had been under surveillance for almost a year before the train attacks, including Fakhet, one of the eight men who died in the apartment. But the surveillance by Madrid's anti-terrorist unit ended in February 2004, the month before the bombings.

Officials of the unit, in documents and testimony, have told the parliamentary inquiry that they stopped their surveillance because of a lack of manpower and a need to shift their focus to a possible ETA attack before the elections and to security for May's wedding of the crown prince.

Other reports handed over to the parliamentary commission reveal how Spain's national police warned as early as the summer of 2003, after a series of simultaneous bomb attacks in Casablanca, that Spain was at increased risk of attacks from Islamic radicals.

Some people who have closely followed the investigations suggest that the bombings were not specifically timed for the election.

In other intercepted telephone conversations reported by El Mundo and broadly confirmed by Spanish authorities as accurate, Ahmed was overheard saying the planning for the March 11 attacks took 21/2 years. That would mean it was in motion well before the election was called, and trying to influence the vote became a secondary objective, if an objective at all.

Some experts believe the elections only provided the attackers a chance to make a bigger impact, but they did not necessarily set out to change the result of the vote. The experts also said that because the police had shifted their focus to the ETA for the elections, the date may have been chosen because it afforded a better chance to execute the plot undetected.

The police "were not looking for Arabs -- they were looking for ETA," said Miguel Angel Bastenier, foreign policy editor at El Pais newspaper. The attackers "took advantage of the fact that there was an election three days later to magnify their attack."

"The terrorists were quite cognizant of the fact that they could piggyback on the publicity of an election," said Bruce Hoffman, a terrorism analyst who heads the Washington office of the Rand Corp. "I don't think they had any idea they could affect the outcome. I don't think they could have orchestrated such a favorable constellation."

Staff writers Dan Eggen and Dana Priest and staff researcher Robert E. Thomason in Washington and special correspondents Pamela Rolfe in Madrid and Sarah Delaney in Rome contributed to this report.

A policeman walks past a hole blasted through a train at the Atocha train station in Madrid, one of four commuter trains that was bombed in March.A closed-circuit television image shows people fleeing moments after a bomb exploded at a Madrid train station in March.