The title says it all: Leaders possess no power.
I'm pretty sure I know what your initial reaction to this statement will be. You will say, "What? No, leaders are powerful!"
The thing is, very few leaders have power on their own. Most leaders do not, for instance, have magical powers or insane acrobatic skills. Leaders are only powerful because people support them.
Imagine a king who rules a country called Entrelonne. The king has all the power because, if someone were to rebel, the army would squash them. But in this situation, the king doesn't have the power -- the army does. The army serves the king, but the king does not personally have the power of the army. If the army were to rebel, the king would be doomed. The king does not, in fact, possess any power whatsoever except that power which his subjects give him.
It's the same with all leaders. Without the support of the people, the leader no longer possesses any power whatsoever. Leadership does not grant power, it gives the service of those who do have power. Of course, leaders can be powerful. The king of Entrelonne, for instance, could secretly be a ninja. But that is the person, not the title. The title of King grants no power to a person.