According to this interesting post on MakingStarWars.net, it’s not who you think it is.
To introduce this idea we are going to focus on a character that appears harmless at first glance but actually holds the power to manipulate not only the people around him but events on a galactic scale. This character is Mas Amedda, Palpatine’s right hand man during the prequel films. When I tell people that he is the second most powerful person in the galaxy I’m met with one of two reactions. Either “Who is Mas Amedda?” or “You’re clearly a crazy person.”