I don't think Bush being duped is the relevant concern here. Bush, from the outset, has confirmed his appreciation that he presides over a country that is split between red/blue -- with the red only slightly dominant. The balance of the Supreme Court was errantly to the blue for the last decade or so. The selections of Roberts and Miers will correct appropriately. We should not expect Bush SC choices to do more than that...MORE would be volatile, not fair. And Bush is a great president.
When the SCOTUS ended its last session, it was made up of seven justices who had been appointed by Republicans and two who had been appointed by Clinton, yet there were only three and a half conservatives (I will give Kennedy the benefit of the doubt and acknowledge that he sometimes voted with the other conservatives). So, the errancy on the court seems to have had more to do with how GOP presidents chose their nominees and less to do with the party who appointed each justice.