Fiction is awash with people who go mad with power, as is history itself. Think of every dictator who ever existed. You might see the extreme version of them when you look them up, the version that was crazy with power and who suppressed his/her people. I can almost guarantee you they didn't start like that, it is something they developed as their reign went on. Maybe they became paranoid about those around them, and tightened control of their state to stop others taking it. Or maybe they became carried away with the idea of being all-powerful, and started to believe they were a god on earth.
Mitchell Hundred, as mayor of New York, recognises this tendency of people in power to go loopy, and he is scared it will happen to him. To this end, he gives devices to his friends Rick Bradbury and Ivan Tereshkov that can stop his own powers. In this way, Mitchell recognises a flaw in himself, and addresses it before it even takes hold. It is part of his internal struggle, and also what makes Mitchell Hundred one of the bets graphic novel characters.
The First Hundred Days is about Mayor Hundred's first days in power. He has to deal with political situations that he just isn't familiar with, like the worst snowstorm ever recorded in the city, an assassin killing off plow drivers, and even budget problems. It is about Mitchell finding his feet in a world that is new to him, and he has to deal with people who work against him, such as the governor. Nothing is easy for Mitchell.
Ex Machina is a comic for a new age. It is the child of Watchmen, taking the superhero story and adapting it and sliding it into modern times. Read Ex Machina if you want a completely new twist on some old themes.
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