From Peter Turchin, professor of ecology and mathematics at the University of Connecticut:
In the US, there is famously a close connection between wealth and power. Many well-off individuals — typically not the founders of great fortunes but their children and grandchildren — choose to enter politics (Mitt Romney is a convenient example, though the Kennedy clan also comes to mind). Yet the number of political offices is fixed: there are only so many senators and representatives at the federal and state levels, and only one US president. As the ranks of the wealthy swell, so too do the numbers of wealthy aspirants for the finite supply of political positions.
When watching political battles in today’s Senate, it is hard not to think about their parallels in Republican Rome. The population of Italy roughly doubled during the second century BC, while the number of aristocrats increased even more. Again, the supply of political offices was fixed — there were 300 places in the senate and membership was for life. By the end of the century, competition for influence had turned ugly. During the Gracchan period (139—110BC), political feuding led to the slaughter of the tribunes Tiberius and Gaius on the streets of Rome. During the next century, intra-elite conflict spilt out of Rome into Italy and then into the broader Mediterranean. The civil wars of the first century BC, fueled by a surplus of politically ambitious aristocrats, ultimately caused the fall of the Republic and the establishment of the Empire.