As top Bush administration officials come before Congress this week to justify the annual $80-plus billion being pumped into Iraq to try to contain a worsening insurgency, new questions have arisen about why the United States invaded that country in the first place. In the wake of remarkable statements by the president, Secretary of Defense Donald Rumsfeld and National Security Advisor Condoleeza Rice that no evidence exists that Saddam Hussein was involved in the September 11^th attacks, the last pillar holding up the administration's justification for invading Iraq has crumbled.

During the Vietnam War, questions about the credibility of the U.S. government's version of the Gulf of Tonkin incident – the event that triggered deep U.S. involvement in the conflict – did not become a major issue until the war started going badly. In the last few months, the same has happened in Iraq. As the chaos in Iraq subtly eroded the president's popularity, the media, pundits and even normally cautious presidential candidates finally found the courage to question whether the administration hyped the threat of Iraqi weapons of mass destruction (WMD). The administration's latest admission should cause the already yawning credibility gap to widen further into criticism about putting American soldiers at risk unnecessarily in faraway lands.

At a recent public forum, Deputy Secretary of Defense Paul Wolfowitz, the architect of the administration's policy in Iraq, listed three reasons for the invasion: concern about Iraq's drive to obtain WMD (that is, nuclear, biological and chemical weapons), Iraq's links to terrorism, and Saddam Hussein's despotic regime that violated human rights.

By Wolfowitz's own acknowledgement before the war, Saddam's evil regime was not, by itself, a justification for the invasion. Also, in the lead-up to the conflict, the administration did not emphasize that rationale as much as the first two reasons. Only after the war, when no WMD were found, did "getting rid of an evil regime" come into its own as a main justification for war.

And at the public forum, Wolfowitz was spinning the WMD justification a bit from what the administration originally argued. Prior to the war, many officials from the administration maintained that the threat posed by such Iraqi weapons programs was so imminent that international weapons inspections had to be terminated – even though the Iraqis appeared to be cooperating – and military actions rapidly initiated. In fact, Vice President Dick Cheney claimed that the administration believed Iraq had "reconstituted nuclear weapons." Even if some evidence of Iraqi weapons or weapons programs is eventually found, the threat was hardly imminent enough to invade the country. It appears that weapons inspections during the 1990s had deterred or at least impeded Iraq from making much progress on reconstituting chemical, biological or nuclear weapons. In fact, an Iraqi scientist buried components for developing WMD until sometime in the future when inspections had ended. Continuing inspections would have undoubtedly sufficed in containing Iraq's weapons programs.

More important, even in the worst case that Hussein had WMD ready to deliver, he did not do so under the most trying circumstances – facing a land invasion that would remove his regime from power or kill him. So during normal peacetime conditions, Hussein would have been unlikely to use such weapons against a superpower with thousands of nuclear warheads.

So the final justification that remained standing was Saddam's support for terrorism. For the most part, administration officials carefully fashioned an implied link between 9/11 and Iraq – never saying directly that Hussein was directly involved. For example, on September 8, 2002, Cheney said, "Come back to 9/11 again, and one of the real concerns about Saddam Hussein, as well, is his biological weapons capability."

But recently Cheney has been less prudent. He alleged that the administration didn't know if Hussein had a role in the September 11th attacks, but then in the same interview said that succeeding in stabilizing and democratizing Iraq would be a major strike at the "geographic base of the terrorists who have had us under assault for many years, but most especially on 9/11." And he also accused Iraq of providing training and expertise in bomb-making and chemical and biological warfare to al Qaeda. Yet professional intelligence analysts have always maintained that any connections between the Hussein regime and al-Qaeda were superficial.

After Cheney's free-wheeling comments, we can interpret the blunt comments by the president and other high-level administration officials – that no evidence exists of a connection between 9/11 and Saddam Hussein – as an attempt at damage control. The administration, stung earlier by intense public criticism that it hyped the threat of Iraqi WMD to justify war, wanted to avoid a repeat performance.

Yet if no link exists between Hussein and 9/11, the collapse of the last and most important pillar supporting the rationale for the war could bring the roof down on the administration's policy toward Iraq. Over time, the administration's implied association between the two has convinced almost 70 percent of the public that the link is real. But now when Americans ask why their sons and daughters' lives and truckloads of their tax dollars have been lost in a remote land, what does the administration have left to tell them?