The bombings were widely blamed on al-Qaida and the vote was later seen as an indictment of Aznar's decision to go to war in Iraq.
Up till now the former Spanish prime minister has been the most high-profile political casualty among the world leaders who led the charge to war last year.
The other men who did so are still in power in their respective countries, but many - like Aznar - will shortly face the judgment of their electorates.
A series of recent inquiries in the United States, the United Kingdom and Australia have blamed intelligence agencies for exaggerating the Iraqi threat in the run-up to the conflict, while effectively exonerating the politicians who took the decision to attack the country.
Nevertheless, the popularity of all the main Iraq war leaders has taken a battering since they toppled Saddam Hussein last year.
And no matter how much they would like to move on and concentrate on their domestic agendas, the controversy they will always be remembered for refuses to go away.
The main cheerleaders for removing Saddam from power have much in common.
Most come from comfortable backgrounds and adhere to similar political creeds.
US President George Bush is a conservative Republican with a religious zeal. British Prime Minister Tony Blair is a deeply religious man who has propelled his once leftist party to the political centre.
And Jose-Maria Aznar is a devout Catholic who dominated Spanish centre-right politics for years.
Aznar paid the electoral price for
backing an unpopular invasion
The other main war leaders, such as Australia's John Howard and Italy's Silvio Berlusconi, are also well-known for dominating the centre-right ground in their respective countries.
The war leaders all have a hawkish agenda, spokeswoman for London-based Stop the War Coalition, Lindsey German, says.
"They are all committed to an aggressive foreign policy and the notion of pre-emptive strikes against so-called rogue states," she said.
Conviction or convenience?
"Blair seems to be the odd one out of them all because he is supposed to represent a centre-left party. But he has proved as hawkish as them all," German told Aljazeera.net.
She added: "I don't think these men opted for war because they were ideologically convinced of its necessity. They all just pitched their political fortunes to the US once they figured out it was hell-bent on war.
"And I also think they felt that war and bombing gave them a certain political kudos which would play well with their electorates."
"These leaders have had their popularity seriously eroded because of the war ... And no matter how many inquiries exonerate them from culpability, it will be the public who ultimately decides if they were
right or wrong"
Stop the War Coalition
German's views are disputed by Gwyn Prins, a politics professor at the London School of Economics, who says the leaders did act out of conviction.
"Bush and Blair, for example, come from very different backgrounds and aren't exactly ideal political bedfellows," he said.
"They just shared this conviction that Saddam was too great a threat to ignore, he needed to be removed and the Iraqi people needed to be liberated.
"The fact is that Saddam had a long-term ambition to acquire nuclear weapons and if he hadn't made the mistake of invading Kuwait in 1990 he would have acquired them by 1993. This is why they went to war."
Some analysts say in launching war against Iraq, the "coalition" leaders established a new doctrine - that of pre-emptive strikes.
"Never before have countries gone to war solely on the basis of intelligence because intelligence is never 100% certain," said Stop the War Coalition's German.
"Most countries go to war when they are under attack. This pre-emptive strike notion is a very dangerous precedent."
But LSE's Prins says pre-emptive strikes have been the norm, rather than the exception, in the history of warfare.
Howard faces a tough re-election
battle in Australia later this year
"The political consensus was that Saddam was a genuine threat and even countries that opposed the war, such as France and Germany, did not provide intelligence to the contrary.
"So the merits of pre-emption should be considered in the context of the threat that was posed."
The fortunes of the war leaders have followed a similar course since last year's invasion.
After the initial swift victory they saw their domestic poll ratings shoot up.
The ratings remained steady for several months as the occupation dragged on, but have recently slipped markedly as troop casualties have mounted.
In the US, the most recent polls have all indicated that President Bush is suffering the worst approval ratings of his presidency.
Polls in May and June show he was considered to be doing a good job by only 30-40% of Americans compared to a high of 70% after Saddam was toppled in April 2003.
Berlusconi's ruling coalition is in
renewed danger of collapsing
In Britain, an ICM poll in a British newspaper on Sunday said 61% of British people did not trust Blair.
Another poll said 30% of people would vote for his Labour party, against 28% for the two main opposition parties - a far cry from the public faith shown in the man when he led Labour to two landslide electoral victories in 1997 and 2001.
And the latest opinion polls show the opposition Australian Labor party up to 12 points ahead of Howard's Liberal party before parliamentary polls later this year.
Analysts say the seeming absence of an Iraqi chemical or biological capability has severely undermined the case for war the leaders initially made.
Questions have also been raised over shocking images of abuses by US forces at Abu Ghraib jail, and the precarious state of Iraqi reconstruction.
"They [the war leaders] just shared this conviction that Saddam was too great a threat to ignore, he needed to be removed and the Iraqi people needed to
London School of Economics
In their defence, the war leaders say the country is no longer under the yoke of Saddam Hussein and is moving towards a democratic future.
And the public in their respective countries seem split over how to judge them.
Despite record low poll ratings, Bush is running neck and neck with John Kerry in the race for the presidency in November.
Blair, meanwhile, may have lost many erstwhile Labour supporters over Iraq, but is still expected to be re-elected prime minister next year.
As for Italy's Berlusconi, while he is not expected to lose power as a direct result of his support for the Iraq war, polls suggest most Italians now want troops to be pulled out of the strife-torn country.
Stop the War Coalition's German believes the war leaders had not counted on the electorate having such a long memory.
"I can't remember a war in my political lifetime which has been such a major issue more than a year after it actually took place. Usually people forget and move on, but people are still very angry about this."
She added: "These leaders have had their popularity seriously eroded because of the war and they will always be remembered for this.
"And no matter how many inquiries exonerate them from culpability it will be the public who ultimately decides if they were right or wrong."