Exploring Voting Blocs Within the Irish Electorate

Irish elections use a voting system called proportional representation by means of a single transferable vote (PR-STV). Under this system, a voter expresses their vote by ranking some (or all) of the candidates in order of preference. Which candidates are elected is determined through a series of counts where candidates are eliminated and surplus votes are distributed. The electorate in any election forms a heterogeneous population, that is, voters with different political and ideological persuasions would be expected to have different preferences for the candidates. The purpose of this article is to establish the presence of voting blocs in the Irish electorate, to characterize these blocs and to estimate their size. A mixture modeling approach is used to explore the heterogeneity of the Irish electorate and to establish the existence of clearly defined voting blocs. The voting blocs are characterized by their voting preferences which are described using a ranking data model. In addition, the care with which voters choose lower tier preferences is estimated in the model. The methodology is used to explore data from two Irish elections. Data from eight opinion polls taken during the six weeks prior to the 1997 Irish presidential election are analyzed. These data reveal the evolution of the structure of the electorate during the election campaign. In addition, data that record the votes from the Dublin West constituency of the 2002 Irish general election are analyzed to reveal distinct voting blocs within the electorate; these blocs are characterized by party politics, candidate profile and political ideology.

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