The varied electoral success of green, radical right, and ethnoterritorial parties across Western Europe is the result of mainstream party strategies. This is the thesis introduced in Chapter 1. Contrary to the dominant literature, I argue that the electoral trajectories of niche parties are not mere reflections of the institutional or sociological characteristics of a country. These successes and failures are rather the result of deliberate attempts by center-left and center-right political actors to quell new political threats and bolster their own electoral competitiveness. Niche party fortunes are, in many respects, the by-products of competition between mainstream parties.

And yet existing strategic theories of party competition prove ill-suited for understanding the nature of interaction between mainstream parties and their neophyte competitors. Unlike their mainstream party opponents, niche parties refuse to compete within the given policy dimensions, instead promoting and competing on new issues that often cut across existing partisan lines. Consequently, mainstream party reactions are not limited to the standard spatial tools of policy convergence and divergence – i.e., movement toward and away from a competitor – on an established issue dimension. Rather, mainstream parties can also alter niche party electoral support by manipulating the salience and ownership of the neophyte's new issue for political competition.

In this chapter, I challenge the standard spatial approach to party interaction by developing a theory of party competition based on this expanded conception of party strategies.