How parties die when voters’ expectations are interdependent. A simulation study

Niklas Harder & Christian W. Martin

The fate of political parties is not only determined by their policy positions but also by the expectations about their electoral success that voters form before an election. In this paper, we are interested in the demise and ultimate death of political parties as a result of voters expecting a party to be unsuccessful.

We draw on an agent based model of expectation formation with interdependent expectations. Voters base their voting decisions on two considerations, namely the distance of their ideal point to a party in the policy space and their expectation about the party’s vote share in an upcoming election. If the second argument in this function is influenced by other voter’s expectations, a downward spiral can emerge that leads to the demise of a party because too few voters expect that party to win even though it could have won based on its policy positions alone. We will explore the conditions under which such a phenomenon can occur and assess the plausibility of the resulting parameter ranges by relating our model’s properties to real world observations.