Broad coalitions, not party size, shape Dutch municipal government

No advantage for the largest party

In multi-party democracies, governments typically emerge from negotiations between political parties following an election. Existing models of coalition formation predict that party rankings should matter: larger parties are expected to have greater bargaining power and therefore a greater chance of joining the governing coalition.

The researchers find no evidence of this in Dutch municipalities. Using election results in which parties narrowly switch positions in the rankings, they examined whether a party’s position actually affects its likelihood of being included in a coalition. They find no causal effect of party rank on coalition inclusion.

A third party is often brought into the coalition

One of the most striking findings concerns municipalities in which two parties together hold a narrow majority. According to the so-called minimal winning coalition hypothesis, these two parties would have little reason to include a third party.

In practice, however, the opposite is largely true. When two parties jointly secure a narrow majority, a third party is included in more than 90% of cases. This points to a strong norm that coalitions should represent a substantially larger share of the electorate than is strictly necessary to secure a majority. Large parties also appear to be favoured for inclusion. Parties that previously formed a coalition excluding a large party are less likely to join the next coalition.

Why do broad coalitions emerge?

The researchers suggest that the institutional design of the Dutch political system may play an important role. In the Netherlands, the largest party does not automatically have a privileged position when coalition negotiations begin. Mayors are appointed by the national government, and political parties must continue negotiating until a coalition is formed.

This differs, for example, from Spain, where the largest party provides the mayor if parties fail to reach an agreement. Such a rule gives the largest party a clear default position and may reinforce a norm in which party size is central. In the Netherlands, the absence of such a default may have allowed a broad-coalition norm to emerge.

What could this mean for democracy?

According to the researchers, broad coalitions may have a potential democratic advantage. A coalition representing a large share of the electorate may be more responsive to the preferences of a broad majority of voters. Broad coalitions may also shift incentives away from policies aimed primarily at individual parties’ supporters and towards policies serving the common good.

The findings also raise questions for future research. The researchers plan to examine whether broad coalitions actually pursue different policies from minimal coalitions. The norm they identify may also help explain why strategic voting for the largest party makes less sense in the Netherlands. This could provide a possible explanation for the highly fragmented nature of Dutch politics.