If the ancient political wisdom is correct that a charge unanswered is a charge agreed to, the Bush White House pleaded guilty yesterday at the Cato Institute to some extraordinary allegations. "We did ask a few members of the Bush economic team to come," explained David Boaz, the think tank's executive vice president, as he moderated a discussion between two prominent conservatives about President Bush. "We didn't get that." Now why would the administration pass up such an invitation? Well, it could have been because of the first speaker, former Reagan aide Bruce Bartlett. Author of the new book "Impostor:...