From the folks at First Read:

The growing Republican CW is twofold. One, Pawlenty appears to be the safest pick, given that one no one is vetoing him. And two, McCain is more likely than Obama to upend the CW with his decision.

CW? We don't need no stinking CW!

Of course one main reason why McCain is more likely than Obama to turn heads is because he's the underdog here. He's also the old, white guy going up against the first black nominee in history. Both facts might require a little something more out of the running mate.

But the point here is not to out-"change" the other guy. The point is to get the best ticket possible, and that means McCain will wait to see whom Obama chooses.