You might benefit from a closer examination of what an oligarchy is and how the US political system functions in the context of campaign finance, lobbyist groups involvement with drafting legislation, and the conveyor between the legislative branch and private industry jobs. If you have the constitution for rummaging through tweedy academic thickets you might also consider reviewing the Princeton papers that deconstruct the US political apparatus and indicate pretty vividly that the US is, in fact, an oligarchy. Lastly, given the combination of wealth inequality in the US and the Supreme Court rulings on money == speech and political influence == speech it's pretty trivial to conclude that money == political influence and the top 0.1% has more of both. To be clear, this is an indictment of both major political parties in the US, as they operate functionally identical campaign finance strategies.