In his book Democracies, Arend Lijphart explores "the operation of actual democracies that approximate the ideal relatively closely--and that Robert Dahl calls 'polyarchies' in order to distinguish them from ideal democracy". Lijphart argues that there are two diametrically opposite models of democracy: the Westminster (or Majoritarian) model and the Consensus model. The basic differences between the opposed models are presented with additional comparisons made between the US and Ruritanian political systems.
 
 

U.S.	Ruritania	WESTMINSTER MODEL	CONSENSUS MODEL
West	Cons	concentration of executive power: one-party bare-majority cabinets	executive power-sharing:  grand coalitions
Cons	West	fusion of power and cabinet dominance	separation of powers
Cons	unicameral	asymmetric bicameralism	balanced bicameralism and minority representation
West	Cons	two-party system	multiparty system
West	Cons	one-dimensional party system	multidimensional party system
West	Cons	plurality system of elections	proportional representation
Cons	West	unitary and centralized government	federalism and decentralization
Cons	West	unwritten constitution and parliamentary sovereignty	written constitution and minority veto
Cons/West in some states	West	exclusively representative democracy