Julius Caesar is a play where the nature of power is discussed on many levels. Here are three ways in which we can think about power in the play.
First and ostensibly, the conspirators believe that Julius Caesar is hungry for power. For example, the people heaped on many titles for him, and most importantly he became a dictator in perpetuity. In the eyes of some, this was tantamount to being a king. In this sense, power causes jealousy and rivalries. In the end, it led to murder.
Second, people like Cassius saw themselves as equals or even greater than Caesar. They wondered what made Caesar great. In their mind, Caesar was no one of special caliber. In light of this, we can say that many people are hungry for power and feel resentment when they do not have it. Power attracts people, we can say.
Another way power is discussed is through the people. If the people are behind you and like you, there is great power. In this sense, influence or the ability to win the favor of people is one of the ways a person gains power.