In a representative democracy not everyone is a member of the government. in fact relatively few people are. so how is representative democracy different from an oligarchy?

Representative Democracy is different from an Oligarcy because Oligarcy is a ruling system in which only a few number of privileged people get the power over ruling and decision-making in a political system and Representative Democracy, is a political system where general public gets the opportunity to select the suitable candidates for the power.
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United states v.  nixon, 418  u.s.  683 (1974),  was  a landmark  united states supreme court case  that resulted in a unanimous  decision  against president richard  nixon, ordering him to deliver tape recordings  and  other subpoenaed materials to a  federal  district  court.