This is not the first time that an authoritative source has declared there was no proven link between Saddam Hussein and al-Qaeda.
Bush and Cheney continue to assert Iraq had links to al-Qaeda
In fact it is almost a surprise that the latest pronouncement, by the 9/11 commission, is even news.
Back in January, the prestigious Carnegie Endowment said: "The most intensive searching over the last two years has produced no solid evidence of a co-operative relationship between Saddam Hussein's government and al-Qaeda."
David Kay, the former chief weapons inspector, came to the same conclusion.
In January the American Secretary of State, Colin Powell, announced that he had seen "no smoking gun [or] concrete evidence" of ties between Saddam Hussein and al-Qaeda.
In fact even President Bush himself, when he was asked baldly in January whether he believed there was a link between Saddam Hussein and 9/11, said "I can't make that claim."
Yet somehow the administration Mr Bush leads has convinced the vast majority of Americans that exactly the opposite is the case.
A poll conducted by the University of Maryland in April found that 57% of Americans believe Iraq was substantially supporting al-Qaeda before the 11 September 2001 attacks or was involved in the attacks themselves. And that number was hardly changed from a similar poll a year earlier.
It has been a subtle operation. Only rarely do administration officials state the case quite as baldly as the Vice President, Dick Cheney, on Monday.
Mr Cheney said Iraq had "long established ties" with al-Qaeda. As usual, he was speaking among friends, in a forum that did not allow critics to question the assertion.
It was Mr Bush who was asked about his vice-president's remarks, at a news conference the following day.
"Zarqawi. Zarqawi's the best evidence of a connection to al-Qaeda affiliates and al-Qaeda," explained the President, referring to the shadowy Abu Musab al-Zarqawi.
"He's the person - remember the email exchange between al-Qaeda leadership and he himself about how to disrupt the progress toward freedom? Saddam Hussein also had ties to terrorist organisations. In other words he was affiliated with terrorism," Mr Bush added.
Nowhere in that response does Mr Bush explicitly draw the link between Saddam Hussein and the 9/11 attacks, but the implication is clear.
"It is one of those things people want to believe," explained Andrew Kohut, of the Pew Research Center for the People and the Press. "You only have to hint at it to get people to jump to that conclusion."
Show of force
Also on Wednesday, a group of distinguished former diplomats and military officers highlighted what they see as the administration's blatant misinformation as part of their condemnation of President Bush's record on national security.
They condemned what they said was a "cynical campaign to persuade the public that Saddam Hussein has links to terrorism and the attacks of 11 September." They stressed: "The evidence does not support this argument."
All of this might be seen as a major embarrassment for any other government, an issue seized on by the opposition. Not here in the United States, though.
When the American public overwhelmingly supported going to war in Iraq, it was not just on the basis of those tenuous links with terrorism.
They believed Mr Bush's wider assertion that this was part of the global War on Terror.
In other words, the best way for America to respond to 9/11 was by a bold exercise of force.
That is what the hawks in the administration believe, as well.
And that is why these latest arguments about the reason for going to war are much less damaging, than the criticism that the administration has not waged it vigorously enough.