Oligarchy?

If memory serves me right, Socrates said that the next step from a democracy was an oligarchy. I believe, it has been a while, his reasoning was that the rich would eventually dominate and control democracy through their power and take over the reins. Of course, it has been quite some time since I last read the Republic but I think they were on to something. It is amazing to think that Socrates was around 500 years before Jesus. It kind of makes Jesus look like a moron.