McCain has snatched the initiative with his Palin pick, which everyone is still reeling to figure out.

One possible approach for Obama is to tack aggressively towards the center, and use the uncertainty surrounding Palin to his advantage.

"Can we really trust Gov. Palin?" the ad might go. "What does she believe? What does she stand for? What would she do if she were in charge of the country? Does she even know? What would she do in response to the Pakistan crisis?"

Palin had one big chance to tell that story to the American people, and she didn't do it. Obama, by contrast, has been in the national spotlight for a long time and has gotten his policy positions out there.

Obama shouldn't abandon the "change" mantra. But maybe he could turn the tables on the shocker pick by casting himself as (ironically) the safe alternative to the "unknown quantity" that is Sarah Palin. A possible campaign slogan here could be: "Obama/Biden: Leadership we can trust."

The risk with this strategy is that Sarah will "pull an Obama" and, throughout the course of the race, will sufficiently address the lingering questions about her agenda. Then the Obama camp would be left holding the bag while McCain/Palin closes the deal.

This will be a tough and exciting fight, no matter what.