McCain's again pushing the Obama-Ahmadinejad line. I think last week's exchange was a short-term win for Obama, in that it drowned out Hillary and pitted him directly against George "30 Percent" Bush. But I think the McCain camp rightly senses this Ahmadinejad stuff is good for them over the longer term. Noam is right that Obama makes a strong case on the substance. And most Americans may well support more engagement with Iran (we need more polling on this). But the notion of a face-to-face meeting is, I suspect, too a little too jarring for most Americans, and extremely easy for McCain to use as a club. Which is why Biden's probably getting it right here and we'll likely see more of the same.

--Michael Crowley