Party Mobilization and Electoral Systems

 By Ignacio Lago (Universitat Pompeu Fabra) & al. 

Research question

Electoral systems scholarship has extensively researched how electoral systems affect voting and parties’ entry decisions. However, we have almost no insight into how electoral systems shape the strategies adopted by political parties in election campaigns. The goal of our study is to explore how district magnitude and the number of districts shape campaign strategies.


When there is a single nationwide district, the payoff in seats of any given increment of votes as a consequence of mobilisation efforts is the same everywhere. Accordingly, both large and small parties will invest more heavily in the most populated areas/provinces given that they can win more votes there. When using a districted electoral system, party mobilisation will be driven less by (district-level) population (i.e., district magnitude) as the rate at which a mobilising party gains seats when it gains more votes differs across districts. But this logic only applies to large parties which face incentives to mobilise everywhere. Given that small parties only have good chances of winning a seat in those districts allocating a high number of seats, they will continue investing their resources in the most populated areas.

Second, as parties exert mobilizational effort the higher the probability of that effort being decisive, small national parties will target densely populated areas regardless of the electoral system. On the contrary, large parties’ mobilizational effort will be more driven by population when using a single national district than in a districted electoral system.


The hypotheses are examined through a quantitative analysis of party mobilisation in the 2009 European election and the 2011 Lower House election in Spain. The 50 Spanish European MPs are elected in a single nationwide district, while the 350 members of the Lower House are elected in 52 districts in which magnitude ranges from 1 to 36. The analysis is focused on three national parties, the two largest, the Socialist Party (PSOE), the Popular Party (PP), and a small one, Union, Progress and Democracy (UPyD). The dependent variable is the number of visits to each district made by the candidate that topped the list in the 2009 European election and the candidate that topped the list put out by the district of Madrid in the 2011 Lower House election. We also use qualitative data collected through a series of semi-structured face to face interviews with members of the campaign teams of the three parties.


We found that varying district magnitudes create different incentives for campaigning. This effect on parties is not universal: smaller parties always target population size or districts with the highest number of seats to be awarded, where their chances of winning are much greater. We find that larger parties alter their strategies depending on the number of districts, mainly by targeting populous provinces in an electoral system with a single national district. When there are multiple districts, large parties will visit more provinces than when there is only one district.

Figure 1. Frequency of visits to each province in the 2009 European election

Figure 2. Frequency of visits to each province in the 2011 Lower House election

Figure 2. Frequency of visits to each province in the 2011 Lower House election


We show that there is not always a change in party mobilisation strategies when there is a change in the payoff of votes to seats. The effect of district magnitude and the number of districts on party mobilisation strategies depends on the size of the political party.

For more information, see:

Lago, Ignacio, Sandra Bermúdez, Marc Guinjoan, Kelly Rowe, and Pablo Simón. “Party Mobilization and Electoral Systems.” Government and Opposition, January 2017, 1–24. doi:10.1017/gov.2016.46.


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