Oligarchy isn't democracy. The Tea Party, however, is. Or, well, "polity", which is to democracy what republic is to oligarchy and monarchy is to tyranny—the form of the system when it WORKS.
Republics, by their nature—being defined as "system with an elite"—always end up ruled solely for the benefit of that elite. The good members of the elite go along with the bad ones to keep peace within their class (we call it "Washington insider"). That's why the US is not designed as a pure republic, but also has popular sovereignty and a strong executive. America is actually a mix of republic, polity, and monarchy; currently, however, the republic is oligarchical and the monarch is a tyrant.