John, like the invasion of Georgia, the grave financial uncertainty brought about by the collapse of two major financial institutions — the contours of which will become apparent as the week goes on —  will tend to make petty, mean political stunts look, well, petty and mean. To the extent Barack Obama thinks his task is to be as aggressive and antagonistic toward his opponent as possible, the intervention of real world events may disrupt his game plan.  If he persists in efforts to belittle both McCain and Palin (in the hopes of either reassuring his base or driving their negative ratings sky high), voters may find that downright odd and inappropriate. At the very least, all those negative messages and ads will be drowned out in the financial news.

To some extent, this may be a welcome interruption for Obama — an unexpected diversion from a path that wasn’t likely to help him steady his drifting campaign. The chance to talk about the “Bush economy” may be just what the doctor ordered. But there again is a trap: the public seems to have accepted that McCain is not in fact a clone of Bush, but rather is his own, mavericky self. If that is the case, a new round of “Bush The Horrid President” messaging from Obama may be irrelevant. (“Yes we agree Bush is horrid, but why should we vote for you?” may be the average voter’s response.)

In short, Obama is finally going to have to make the argument why voters should trust him and not McCain, why the Obama model of expanded government and higher taxes is the way to go. And McCain finally has his shot: to explain what his economic vision is and to make the case that high taxes, big governement, and protectionism is a recipe for disaster.

Hey, we might actually have a nice meaty policy argument. We’ll learn a lot about the two candidates’ level of confidence in their own message by which one welcomes that fight and which one turns tail.