I agree with idea that simple people should be the highest supervision over politicians. Well, it is just like that in democracy, unfortunatelly it doesn't work - but I don't think that because all people are corrupted. They aren't - truth is always a little bit more complicated.
Lots of people are just too stupid to distinguish evil and good or it is simple to deceive them. Lots of people just don't care - because they do not undestand politics (who really does? ) or they just want to live simple lifes (IMO not bad). And yes, lots of them are corrupted (but definitelly not all).
There are one other aspect of all this. What we consider as good and as bad? It is just our subjective point of view. Do you think that people of (for example) Islamic State consider themselves as bad? IMHO they don't. Maybe they think about themselves as saviors and warriors of justice (exactly as our politicians). Another example. Do you know Star Wars? Great Jedi warriors, keepers of the peace, featuring as good. Oposite of them are Sith Lords, generally considered as bad. But what is the final goal of the Sith? Peace, exactly as for Jedi. It is just fictional story, but reflects the truth - the concept of evil and good (which is so often used in discussions even on this forum) is just reflection of our own selfish and subjecive valuation of what we see around us.
And what I want to say? Maybe bad politics are just trying to survive, to win endless fight of evolution in overpopulated Earth just like everybody. They choose tools as they did maybe because they suffer from messiah complex or maybe because it is very pleasant to have a power. It looks like a irrelevant detail, but it helps from going crazy - there are no bad nor good and maybe all this is natural as whole evolution.