Unlike a
one-party system (or a
dominant-party system), a multi-party system encourages the general
constituency to form multiple distinct, officially recognized groups or alignments-of-interest, generally called
political parties. Each party, especially but not only during election campaigns, competes for votes from the
enfranchised constituents (those allowed to vote) of the relevant polity. A multi-party system prevents the leadership of a single party from controlling a single
legislative chamber, at least not without ongoing challenge from other 'opposition' or 'minor' or 'minority' parties. A special case of a multi-party system where only two parties have a realistic possibility of winning an election is called a
two-party system. A two-party system requires voters primarily to align themselves in (two) large blocks; these blocks are sometimes so large that they cannot agree internally on appropriate policies or even on overarching or organisational principles. Some theories argue that this gives
centrists (including those in each of the two main blocks or parties) more opportunities to gain control, though this is disputed and depends largely on the features of elections (e.g., compulsory voting; political fundraising regulations) and institutions, and the tradition of rule of law, in the relevant polity. On the other hand, if there are multiple major parties, each with less than a majority of the vote, the parties are strongly motivated to work together, over time, to allow for the formation of working governments, or indeed any (democratically justifiable) government. Multi-party systems can also tend to promote centrism, privilege coalition-building, slow down or stimie major policy pivots, moderate policy adventurism, and discourage polarization, especially polarization of the leader of a coalition (polarization here referencing an ideological movement to the extremes, or 'poles' (edges), of political opinion by political parties—and thus by polities and their leaders). == By country ==