Criticism and Alarm Bells
When a leader becomes ultra-sensitive to criticism or dissent, that is a sign of decline. Confident leaders can take a punch. They can also scan opinions which they regard as ridiculous in order to see if the fog contains anything of merit.
Sit in on a staff meeting and watch how anything that goes against the grain is treated. If there is a rush to suppress or, worse yet, a reluctance by the participants even to bring up a mildly-critical point, alarm bells should go off. Strained efforts to justify every action should also be scrutinized.
Aside from the questions of competence and openness which these raise, there is also an ethical issue. A leader who will squelch dissent will also cover up. One who will bridle at criticism will also twist facts and deceive.
More than one alarm bell should be ringing.