To say that John McCain has thrown the dice by picking an untested unknown is an understatement. Which raises the question: Even if Sarah Palin does well, does this cause some voters to consider him a bit of a loose cannon? There can be a fine line between being a maverick and being a bit of a nut and with this choice, McCain runs a risk of coming very close to the line.
This isn't to say she might not prove to be a masterful pick. But there's a way in which right now, Barack Obama looks like the more conventional, reassuring figure. That's not what McCain wants voters to think -- not now and especially not in November.