the Iron Law of Oligarchy. That is the thesis that all forms of government despite their nominal structure effectively act as an extension of a small elite. Unquestionably political science research has shown that this is true of American democracy. When upper and lower/middle class disagree on policy, the upper class virtually always wins (see link below). If you accept the basic evidence that America already acts in a very non-democratic way, then wanting to formalize that structure is not an indefensible position.
http://econlog.econlib.org/archives/2012/09/why_is_democrac.html
http://econlog.econlib.org/archives/2012/09/why_is_democrac.html