George Bush can pick the most radical right wing ideologue and demand that the right stand up and fight every inch of the process for confirmation. A candidate without the slightest hint of moderation would be an open invitation to the base to put up or shut up.
Unfortunately, Bush has never seen fit to rub anyone's nose in their own crap, so expect a moderate conservative (is that possible?).
The person whose opinion I would most like to have for a recommendation to the Court is Judge Roberts.