The US political system is basically an arena where countless special interest groups battle it out to grab as many goodies as they can from the the horde of Federal loot plundered from taxpayers. Some leverage votes (democracy), others leverage cash (oligarchy).
Wouldn't leveraging money be a plutocracy?
True. Thinking about it some more, I'd say the US is a combination of democracy, plutocracy, and oligarchy. The former two account for the majority of legislation and programs, but the latter also exists when you consider the minority of policy manufactured by the technocratic elite of policy wonks, think tankers, etc.