The next time a president sets out to convince Congress, the American public, and a new coalition of the willing to take up arms, the credibility gap will be wider - unless weapons of mass destruction actually turn up in Iraq.
It's a concern now voiced on both sides of the aisle as the search for evidence of chemical, biological, and nuclear weapons has come up empty for eight weeks after the end of major combat operations in Iraq.
"If we are going to hit first, based on perceived dangers, the perceptions had better be accurate," said Sen. Robert Byrd (D) of West Virginia in a statement on the floor of the Senate earlier this week.
The British Parliament is giving Prime Minister Tony Blair an even rougher time. Members of his own Labour Party and cabinet charge that Mr. Blair exaggerated the immediate threat posed by Iraq and deliberately distorted prewar intelligence estimates.
The parallel probes now under way on both sides of the Atlantic foreshadow a more difficult path if and when a US president tries to make the case for a preemptive use of force against another country. Skepticism will likely be higher not only in Congress, but with overseas allies, the press, and American public opinion, analysts say.
In Washington, Democrats in particular say that a continued failure to confirm those Iraq intelligence estimates will make any future case for preemption much tougher. "Until they sort it out, it well be very difficult for the president to get that kind of credibility again," says Sen. Christopher Dodd (D) of Connecticut, one of 28 Democrats who voted last October to authorize force in Iraq.
The question is not merely academic. The possibility of a nation such as Iran moving to develop nuclear weapons could again test the ability of US intelligence services, and the credibility of the executive branch in using that intelligence.
For the US public - which for now has not withdrawn its support for the war in Iraq - ongoing deaths of US troops may do more to discourage future military forays than a failure to find weapons of mass destruction in Baghdad.
Experts say it's the British prime minister who will pay the larger political price for a gap between claims of an imminent Iraqi threat and the results in the search for weapons of mass destruction on the ground.
"I would think that Tony Blair will never be quite as popular again as he was before the war," says Michael O'Hanlon, senior fellow at the Brookings Institution. "Bush overall painted a more dire picture, but Saddam never tried to assassinate a former British prime minister. And the feeling of a responsibility for being the world's policeman is not as strong in Britain as here."
The US Congress, for its part, is conducting a much less public "review" of the evidence used by the Bush administration to make the case for war. Sen. Pat Roberts of Kansas, who chairs the Senate Select Intelligence Committee, has even resisted the use of the term "investigation" as too "pejorative."
For the past two weeks, members of the intelligence committees in both the House and Senate have been working their way through 10 volumes of national intelligence documents on Iraq's weapons threat. Their hearings are closed and the documents are still classified.
"We're all looking to see how good the intelligence has been, ... [and] if there has been any outside interference in the process," says Rep. Porter Goss (R) of Florida, a former CIA operations officer who chairs the House Select Intelligence Committee. "So far, I've seen no evidence at all [of interference], nor have the Brits."
Earlier this month, Mr. Goss and Jane Harman of California, the ranking Democrat on the committee, outlined a plan for reviewing the evidence, including the possibility of open hearings and an unclassified summary of findings for the public.
THIS week, Rep. Ron Simmons (R) of Connecticut called on Bush to release a paper on Iraqi weapons capabilities, including photographs and testimony from scientists. Mr. Simmons, another former CIA operations officer, has had access to the documentation. He says that what he has read is not at variance with the case President Bush made to the American people for war. "I am confident they are operating honestly. But I'm not confident they are operating at full capacity.... Our human sources of intelligence have been seriously degraded."