But the officials offered no evidence to support their charge that “the highest levels of the Iranian government” had authorized smuggling these weapons into Iraq for use against American forces. Nor could they adequately explain why they had been sitting on this urgent evidence since 2004. The only thing that was not surprising was the refusal of any of the briefers to allow their names to be published. Mr. Powell is probably wondering why he didn’t insist on the same deal.

We have no doubt about Iran’s malign intent. Iran is defying the Security Council’s order to halt its nuclear activities, and it is certainly meddling inside Iraq. But we are also certain that the Iraq war has so strained the American military and so shattered this president’s credibility that shrill accusations and saber rattling are far more likely to frighten the allies America needs to contain Iran’s nuclear ambitions than to change Tehran’s behavior.

If Mr. Bush is truly worried about Shiite militias killing Americans in Iraq  and he should be  he needs to start showing this evidence to Iraq’s prime minister, Nuri Kamal al-Maliki. The president needs to demand that Mr. Maliki stop protecting the militias and make it clear that there will be serious consequences if he continues to refuse.

If Mr. Bush is truly worried about Iran fanning Iraq’s ever more bloody civil war  and he should be  he needs to stop fantasizing about regime change and start trying to find a way to persuade Iran’s leaders to help rein in the chaos in Iraq.

And if Mr. Bush is worried that Americans no longer believe him when he warns of mortal threats to the country  and he should be  he needs to start proving that he really understands who is most responsible for the Iraq disaster. And he needs to explain how he plans to extricate American troops without setting off an even bigger war.