The comparative study of party politics dedicates a large space to analyses of the party positions on certain issues or dimensions. But with the exception of Meguid (2005, 2008) and few other pioneers, party positions have seldom been used for the understanding of party competition. The position of a party cannot be apprehended independently from the positions of the other actors within the same party system. This paper therefore intends to demonstrate that political parties compete on certain public policy issues (and not on others) and that the arrival or disappearance of new competitors (new parties, party splits, etc.) as well as the appearance of new issues lead to a redefinition of the party competition. Different patterns of competition will be identified, depending on the issue, the time frame and the party system environment. This paper relies on quantitative data from the content analysis of party manifestos in Belgium. All party programs of Belgian parties in the Parliament between 1977 and 2007 have been coded according to the CAP (Comparative Agenda Project) coding frame. Statistical analyses will allow us to position these parties on a large set of public polity issues, to identify niche parties and their eventual property on some issues, and to compare their positions over time, between parties and between linguistic communities. More specifically and following the emergence and the electoral success of green, regionalist or extreme-right parties, this paper will study ideological convergence and the contamination of issues such as environment, law and order or decentralisation on the mainstream parties’ manifestos and – a party manifesto being a zero-sum game – which issues have been put aside.
