And now for some real political drama.

On the trail today in South Dakota, Barack Obama will keep up the pressure on John McCain for wrongly saying that the troop numbers in Iraq are now at "pre-surge" levels, using McCain's refusal to admit error over the gaffe as yet another way to strap him to George W. Bush. From the prepared remarks sent over by the Obama campaign:

We all misspeak sometimes. I've done it myself. So on such a basic, factual error, you'd think that Senator McCain would just admit that he made a mistake and move on. But he couldn't do that. Instead, he dug in. And the disturbing thing is that we've seen this movie before -- a leader who pursues the wrong course, who is unwilling to change course, who ignores the evidence. Now, just like George Bush, John McCain refused to admit that he made a mistake. And that's exactly the kind of leadership that we've had through more than five years of fighting a war that should've never been authorized, and should've never been waged.

We don't need more leaders who can't admit they've made a mistake, even when it's about something as fundamental as how many young Americans are serving in harm's way.

It's clear that McCain's campaign misplayed this one. He could simply have said, "Yeah, yeah, yeah, I misspoke. I meant to say we're in the process of drawing down to pre-surge levels. Sorry. Now can we get back to the issues?"

But instead, the McCain camp tried to turn this into a debate about "verb tenses" -- the sort of error more often committed by Dems, and more often exploited by Republicans. Who knows how big an impact this will have, but the fact that Obama camp isn't letting up on this will cheer Dems wondering how aggressive the Obama team will be in the general.