President Bush’s pre-war exaggerations of the strength of the intelligence that Iraq had an active nuclear weapons program and large stockpiles of biological and chemical arms were neither "lies" nor as far from being true as partisan critics suggest. His now-infamous assertion in his January 28 State of the Union address — that the British government "has learned that Saddam Hussein recently sought significant quantities of uranium from Africa" — would have been quite accurate had he crossed out "has learned" and inserted "believes." More recently, Bush could have repaired the damage to his credibility by taking responsibility for any overstatements or errors about details, while carefully explaining why the case for war was and remains strong.

This is not the approach that Bush has taken, however. Instead, he has accused his critics of "revisionist history" while retroactively revising his own pre-war claims. He and his aides have passed the buck with unseemly eagerness to CIA Director George J. Tenet for Bush’s now- inoperative uranium-from-Africa claim; in fact, the CIA, despite pressure from administration hawks to tailor its intelligence to their policy goals, had repeatedly warned the White House that the evidence was shaky. And Bush has uttered a succession of bald untruths and evasions reminiscent of Bill Clinton, except that Clinton would have been much more artful.

On July 14, for example, Bush said in an impromptu press conference that "subsequent to the [State of the Union] speech, the CIA had some doubts" about the uranium-from-Africa intelligence. But in fact, the CIA had expressed doubts months before that speech, as any casual news consumer knows now, whether or not Bush knew it on January 28.

Moments later, Bush added: "The larger point is, and the fundamental question is, did Saddam Hussein have a weapons program? And the answer is, absolutely. And we gave him a chance to allow inspectors in, and he wouldn’t let them in. And, therefore, after a reasonable request, we decided to remove him from power." (Emphasis added.) This was outlandishly, transparently false. Saddam allowed Hans Blix and his team of United Nations inspectors into Iraq in November. It was Bush’s determination to invade — not Saddam’s actions — that cut the inspections short.

Then there was Bush’s pathetic assertion on May 29, in an interview with Polish television, that "we’ve found the weapons of mass destruction. You know, we found biological laboratories." But the trucks to which Bush was referring contained neither biological agents nor evidence that any such weapons had ever been there. And whether they were mobile laboratories for the manufacture of biological weapons is still a subject of dispute among intelligence experts.

What are we to make of such hokum? Had it come from Clinton, Republicans would have accused him of deliberately deceiving gullible voters, and so would I. In Bush’s case, another hypothesis seems plausible: a disturbing ignorance of and insouciance about critical facts, combined with a reflexive urge to duck accountability. "The characteristic Bush II form of dishonesty," Michael Kinsley wrote more than a year ago, with perhaps a pinch of hyperbole, "is to construct an alternative reality on some topic and to regard anyone who objects to it as a sniveling dweeb obsessed with ‘nuance.’ "

Whatever Bush’s mental process (and I don’t think it is captured by the word "lying," now so fashionable among apologists for Clinton’s perjuries), the more the president works at creating his own Iraqi-WMD credibility gap, the harder it becomes to take his word for anything.

I say this with great regret, because I believe that in these terrifying times we desperately need this president — and the next one, and the one after that — to be effective in fighting terrorist enemies and rogue regimes. Otherwise, their quest for doomsday weapons is all too likely to end in the murders of millions of Americans. And I fear that the Democratic presidential contenders (with the possible exceptions of Gen. Wesley Clark, a noncandidate so far, and Sen. Bob Graham of Florida) and their party may not be up to the job of using military force as assertively as necessary to avert such catastrophes.

Bush is plenty assertive. But he also needs to be believable, especially in the supremely serious matter of pushing for preventive wars. Suppose, for example, that the president tells us next week that Iran is starting to make nuclear bombs for sale to Al Qaeda, or that North Korea’s nuclear program "poses an imminent danger of nuclear weapons being detonated in American cities," as former Clinton Defense Secretary William Perry warned in a recent Washington Post interview.

Will the world, or even the nation, believe a president who has so recently asserted that Saddam wouldn’t let inspectors in, that the CIA’s doubts about his uranium-from-Africa claim had arisen "subsequent to the speech," and that "we’ve found the weapons of mass destruction"? Republican hawks miss the point when they ask, as Newt Gingrich did last month, "Does even the most left-wing Democrat want to defend the proposition that the world would be better off with Saddam Hussein in power?" The point is that the president of the United States should tell the truth, not least because our security depends upon his credibility.

Bush’s mangling of established facts has emboldened his critics and the media to overstate the importance of his pre-war overstatements of the WMD evidence, some of which postdated the lopsided House and Senate votes in October authorizing Bush to invade Iraq. This is the view not only of Republican partisans but of some Democrats, including Philip Bobbitt, who served President Clinton as a senior National Security Council strategist. Bobbitt warns that "you guys" — the media — dangerously distort the big picture by focusing obsessively upon presidential misstatements.

"The nuclear threat posed by Saddam was very real," says Bobbitt, even if the uranium-from-Africa claim and some other intelligence cited by the administration were wrong. "He was well known to have enormous riches from illegal oil sales, has long sought nuclear weapons, and steadfastly refused comprehensive U.N. surveillance that might give warning. One never knew when we might wake up to find he had bought or developed a nuclear device that would put these depredations completely beyond redemption."

Indeed, if one thing has become clear since the war, as Washington Post columnist Jim Hoagland has stressed, it is that the intelligence community did not know enough "to predict with accuracy the intentions and capabilities of Saddam Hussein and his regime." Saddam gave Bush ample reason to assume the worst, and thus to move in before Saddam became too strong.

The media focus on Bush’s credibility "is bewildering," adds Bobbitt, who is more forgiving of presidential misstatements than I, perhaps because he has an insider’s view of the torrent of information and decisions every president must process every day. "President Bush’s pre-war statements about WMD were, in the main, merely stating the obvious: Every major leader, including (Jacques) Chirac and (Vladimir) Putin, and every major intelligence service was, and remains, convinced that Saddam Hussein acquired and did not wholly destroy large stocks of WMD. Whether the president’s rhetoric was as careful as one might wish or not, the big picture ought not to be very controversial, and he is basically a big-picture guy. Nobody ever thought George W. Bush was a detail man, and the press has long known that net assessments are seldom unanimous in intelligence community."

Bobbitt, who also predicts that former Iraqi officials and scientists will provide ample evidence of an active WMD program once they no longer live in fear of Saddam’s return, adds valuable perspective to the current uproar. But the media can hardly be expected to stop focusing on Bush’s credibility until Bush stops making demonstrably untrue statements.

This is not to join The New York Times in urging the president to make a public apology for his past misstatements. "Leading a war effort is not made easier by constant second-guessing by the president of his own actions and public retrospective reassessments of those actions," as Bobbitt says. "For one thing, it embarrasses allies, as it has Tony Blair. For another, it saps public confidence in the president’s leadership. Regret is a sentiment best left to a president’s memoirs." Besides, Bobbitt adds, Bush "did not seriously err."

But err he did. And leaders do themselves no credit when they pile misstatement upon misstatement or seek to shift all blame to subordinates for everything that goes wrong. If George Tenet can say, "I am responsible for the approval process in my agency," George W. Bush should be able to say, "I am responsible for the approval process in my administration."