There is considerably more to building coalitions than simple arithmetic, explains Bettina Petersohn. Prospective prime ministers may have an eye on strategy as much as stability and they would do well to consider the impact of post-election deal making in the devolved assemblies.
There is a widely-held view that single majority governments are the norm for the UK. The outcome of the 2010 elections and the resulting coalition government are treated as an accident to be rectified the next time. However, the rise of new parties and the different party systems in the devolved territories reduces the chance of a single party winning a majority of seats - and coalition governments become more likely even in the UK. Contrast this with countries where PR is used for parliamentary elections and where coalition governments are common. Experiences from these countries shed some light on why parties form coalitions, with whom are they more likely to govern together, and how it matters for the stability of governments.
One way to distinguish different types of coalitions is to look at the size of the majority the cabinet can control in parliament. If we assume that parties are interested in getting into office and exercising as much power as possible, it makes sense to include the fewest number of parties possible to secure a majority in parliament. This approach is called a minimal winning coalition. The more parties included in government, the fewer cabinet posts for each one and the less power is available to pursue the parties’ goals.
However, arithmetic is only part of the story, policy positions and whether the party leans to the left or right of centre are also a factor. For example, the Greens in Germany are closer to the Social Democrats (SPD) than to the Christian Democrats (CDU). Coalitions between Social Democrats and Greens operated between 1998 and 2005 at the federal level, and several times in a majority of Lander. Although prominent members within the CDU and the Greens have repeatedly advocated in favour of a so called 'black-green' coalition between the two parties, it has been used predominantly for local councils and only exceptionally at the Lander level.
Political strategy also affects the choice of governing partners. Having ruled out and an alliance with the German socialist party Die Linke, the Social Democrats became the junior partner in a grand coalition with the Christian Democracts after the federal election of 2013. This is despite the fact that a left coalition of SPD, Greens and Linke had a majority in parliament in which the SPD could have nominated the Chancellor. This approach would seem to contradict the minimal winning coalition concept.
When looking at coalitions in different countries over time, we find numerous examples where more parties than necessary participated in government - so called oversized coalitions. They have been formed in the context of exceptional circumstances, for example Churchill’s war time cabinet, or when the political system is regarded to be under threat from anti-system parties. If governments wish to change constitutional legislation and a broader consensus is required to pass these changes, it might also be easier to achieve these changes with an oversized coalition.
Furthermore, oversized coalitions might fit with the political culture of a country or serve to accomodate different linguistic or cultural groups. The consensual style typical in Switzerland is reflected in an all-time Grand coalition with the four major parties participating in government throughout the decades since the Second World War (interrupted only between 1955-1959). The linguistic division in Belgium finds expression in coalitions that unite the sister parties from the two linguistic groups - so if Francophone Socialists participate, the Flemish Socialists do as well - leading to oversized coalitions. With the UK’s rather adversarial political culture, such grand or oversized coalitions seem unlikely in the UK even though some may think that planned constitutional changes would benefit from a broader consensus.
Minority cabinets, usually comprising the largest party in parliament (either alone or with other parties) requires negotiating opposition support for each bill. We speak of a tolerated minority government if one of the opposition parties agrees to lend its support on a more stable basis. Again, political culture and the procedure by which governments are instituted have an impact on the likelihood of minority cabinets. In Germany, for example, a cabinet has to be instituted by a majority vote in parliament making minority cabinets less likely than in the UK where such a vote is not required. Minority cabinets have formed almost 30% of all coalitions in western democracies since the Second World War. They are still regarded to be the most problematic form of government in terms of stability or success in achieving majorities for legislative initiatives.
In countries divided by languages or national identities, nationalist parties supporting a minority government might use that position to make demands for more autonomy. The idea of the SNP supporting a minority Labour government in London has raised concerns about the potential consequences. Research about Spain however has shown that regional nationalist parties supporting minority government at the centre have contributed to its success if the nationalist party is in need for support at the devolved level because it cannot command a majority in the region. Support for the minority government at the centre can then be exchanged for support at the regional level if both parties make effective use of the opportunities that multilevel politics offer. In the UK context that means: a Labour minority government in London supported by the SNP will be more successful if the SNP needs the support of Scottish Labour to govern in Scotland. As long as the SNP governs alone in Scotland, however, a deal in London is less likely to deliver stability.