Party Systems

Duverger's theory

states that the size of a country's party system depends on the complex interplay of both social and institutional factors. Social divisions create the "demand" for political parties, and electoral institutions then determine the extent to which this demand is translated into parties that win votes (electoral parties) and parties that win seats (legislative parties)

Duverger's law

states that single-member district plurality systems encourage two-party systems

Duverger's hypothesis

states that proportional representation electoral rules favor multiparty systems

Effective number of electoral parties

is a measure of the number of parties that win votes.

Effective number of legislative parties

is a measure of the number of parties that win seats.

Ethnic party

champions the interests of one ethnic group exclusion of others, and does so as a central component of its mobilizing strategy.

Freezing hypothesis

States that Western European party systems became frozen following the extension of universal suffrage in most countries during the 1920s.

Four Cleavages based on Lipset-Rokkan Hypothesis of party formation

Center-periphery; industry-agriculture; state-church; owners-workers

Mechanical effect of electoral laws

refers to the way votes are translated into seats. When electoral systems are disproportional, this punishes small parties and rewards large parties.

Strategic effect of electoral laws

refers to how the way in which votes are translated into seats influences the "strategic" behavior of voters and political elites.

Multiparty system

is one in which more than two parties have a realistic chance of holding power.

One-party dominant system

is one in which multiple parties may legally operate but in which only one particular party has a realistic chance of gaining power.

Two-party system

is one in which only two major political parties have a realistic chance of holding power.

Party identification

is an attachment to a party that helps citizens locate themselves on the political landscape.

Party Volatility

a measure indicating a change in the share of party vote in several consecutive elections

Party System Institutionalization

is an indicator of the stability of parties' electoral strength, their rootedness in the society and public recognition of their necessity (legitimacy).

Median Voter Theorem

expects parties to compete for centrist voters and move ideologically closer to the centrist preferences

Direction Voting Theory

expects parties to take extreme positions to clearly communicate to voters the general direction of their policies

Valence Theory of Voting

expects parties to attach emotion-laden labels asserting their own competencies and deriding the poor competence of their competitors