There are many different reasons why people seek power in society. Citizens like to believe that their leaders reach high-ranking positions because their leaders have natural leadership abilities, and furthermore, that leaders have a desire to use their gifts to help others. Unfortunately, this belief is true only in exceptional cases. Most often, the reason for people becoming authority figures in society is due to their desire for greater control over others. Most authority figures gain their positions for exactly this reason. If you examine abuse, political or otherwise, it is easy to see the connection between the power drive to abuse and toward creating abusive relationships.
The worst category of abuser consists of the sociopaths, and a sociopath will climb to a position which maintains his power over others. A sociopath is a person who has very few normal human emotions, but who has learned to fake emotions to hide his mental condition, and to better manipulate ("lead") others. A true sociopath's character, which is often carefully hidden from public view, has only two genuine emotions: rage and jealousy. The classic sociopath is an intelligent and manipulative being, who has a superficial charm, and an inflated ego. He does not have a true conscience because he is unable to experience any true remorse for his actions, and he is unable to empathize with the suffering of others. He has no true remorse for any of the things that he has done immorally, unethically, or illegally. He may either rationalize his wrong-doing, or be completely indifferent. Sociopathology is where the term "emotional problems" comes from, because the evil behavior of these people stems from their lack of emotions necessary for developing a conscience. They tend to become serious problems for the rest of us as the monsters of society. The sociopaths who reach positions of power have learned to hide their character from most, and silence the rest. While power may indeed corrupt, most people in power were actually already corrupt before seeking power.
People with at least some sociopathic tendencies are the ones who generally make their way into positions of power. As an abuser, he must exert power and control over others to feel complete in himself, and ironically to compensate for his overwhelming sense of powerlessness. This is generally due to a childhood in which he was deprived of the ability to control the events around him, and so he tries to control others in order to compensate for his own somewhat panicked sense of powerlessness. As a sociopath, he shows no remorse for the actions he takes to maintain his power. Often a sociopath will issue needless edicts to reassure himself that he still has control, or to remind others of it. A sociopath will never have enough power, for his hunger to control becomes stronger as he gains more. It very much like a drug addiction, or the insatiable greed seen amongst the wealthy.