President Bush keeps his cabinet and other top people on a short leash--or tries to. Here's why some appointees succeed and others don't--plus, how the current Bushies have done so far. AFTER THE OVAL OFFICE, the most impressive chamber in the White House is the Cabinet Room. High-backed leather chairs, each engraved with the name of a Cabinet secretary, ring a massive oval mahogany table. The men and women who oversee the vast federal bureaucracy can sit there and gaze out at the Rose Garden. If appearances count, this should be the power center of the executive branch. But as...