Obama cites John Kennedy meeting Nikita Khrushchev as another example of what he wants to emulate. Really? That Vienna summit of a young, inexperienced, untested American president was disastrous, emboldening Khrushchev to push Kennedy on Berlin -- and then near fatally in Cuba, leading almost directly to the Cuban missile crisis. Is that the precedent Obama aspires to follow?

A meeting with Ahmadinejad would not just strengthen and vindicate him at home, it would instantly and powerfully ease the mullahs' isolation, inviting other world leaders to follow. And with that would come a flood of commercial contracts, oil deals, diplomatic agreements -- undermining precisely the very sanctions and isolation that Obama says he would employ against Iran.

As every seasoned diplomat knows, the danger of a summit is that it creates enormous pressure for results. And results require mutual concessions. That is why conditions and concessions are worked out in advance, not on the scene.

What concessions does Obama imagine Ahmadinejad will make to him on Iran's nuclear program? And what new concessions will Obama offer? To abandon Lebanon? To recognize Hamas? Or perhaps to squeeze Israel?

Having lashed himself to the ridiculous, unprecedented promise of unconditional presidential negotiations -- and then having compounded the problem by elevating it to a principle -- Obama keeps trying to explain. On Sunday, he declared in Pendleton, Ore., that by Soviet standards Iran and others "don't pose a serious threat to us." (On the contrary. Islamic Iran is dangerously apocalyptic. Soviet Russia was not.) The next day in Billings, Mont.: "I've made it clear for years that the threat from Iran is grave."

That's the very next day, mind you. Such rhetorical flailing has done more than create an intellectual mess. It has given rise to a new political phenomenon: the metastatic gaffe. The one begets another, begets another, begets ...