By Dylan Difford. Dylan is a researcher specialising in elections and voting systems.

In this bumper year of elections, Portugal is the first European democracy to be heading to the polls to elect a new parliament. This was a little unexpected; the Socialists won a majority just over two years ago and had not lost the confidence of parliament. But Portugal, like France, is a semi-presidential country, where the president – currently Marcelo Rebelo de Sousa of the opposition PSD – holds some genuine executive power. After a scandal hit the prime minister António Costa last year, Rebelo de Sousa chose to call a new election rather than form a new government. How will this Sunday’s election work and what can Portugal teach us about the importance of constituency size under PR?

Portugal’s voting system

Since democratisation in the 1970s, Portuguese elections have taken place using a straightforward version of constituency-based Party List PR. The electoral process is incredibly simple, with a lot of similarities to the system used to elect British MEPs between 1999 and 2019. Voters choose a single closed party list (i.e., the list of candidates and their order of election is fixed by the parties), and seats are allocated to parties according to the D’Hondt method, with no fixed electoral thresholds (i.e., there is no share of the vote parties have to reach in order to win seats).

It is at the level of the constituencies themselves where the Portuguese system becomes more distinctive. The Assembly of the Republic contains 230 MPs, elected from 22 constituencies. 20 of these are within Portugal itself and correspond to the 18 districts of Portugal and the autonomous regions of the Azores and Madeira, with the number of seats each constituency elects dependent on the number of voters on the electoral roll. The other two constituencies, which return two MPs each, are chosen by Portuguese citizens living abroad, one representing those living in Europe and the other the rest of the world.

Comparatively, these constituencies are at the smaller end of the scale in terms of district magnitude (how many MPs each elects). The median Portuguese constituency elects seven MPs, similar to neighbouring Spain’s five or Norway’s six, but considerably less than the higher medians of Belgium (15), Denmark (14) and Finland (16). While still allowing for a reasonable level of overall proportionality, these smaller constituencies effectively favour the larger parties, making it possible for one to gain a majority in the Assembly from vote shares in the mid-40s – demonstrating the small trade-offs between ‘pure’ proportionality and local representation.

Effects on the party system

It is largely because of these small constituencies that the two main parties in Portugal – the centre-left Socialist Party, and the confusingly named centre-right Social Democratic Party (PSD) – have dominated for much of the last fifty years, winning 75-90% of seats between them in recent elections. As such, the two main parties have tended to form single-party administrations, such as the current three-term Socialist government, which started as a minority in 2015, before gaining a majority in 2022. However, the PSD has also occasionally formed coalitions, including pre-election alliances, such as at this election, with the conservative CDS-People’s Party.

Filling out the rest of the Assembly has long been the left-wing CDU and Left Blocs, with a handful of new, smaller parties gaining representation in the last decade, including Liberal Initiative, environmentalists PAN and populist Chega. Nonetheless, there is little doubt that the next prime minister will be either PSD leader Luis Montenegro or new Socialist leader Pedro Nuno Santos.

What lessons should we in the UK draw, if any?

On the one hand, the Portuguese iteration of List PR is a reminder that proportional systems can, if so designed, seamlessly combine small constituencies that reflect familiar geographies with election results that reasonably reflect public opinion, underpinned by a pluralistic party system. Wanting local constituencies does not inevitably lead to grossly distorted results and artificial ever-changing constituency boundaries, as we have under First Past the Post.

However, Portugal’s closed list system is not perfect, with the vast differences in district magnitude between urban and rural constituencies raising the most questions. At one end you have the big cities like Lisbon and Porto, who elect 48 and 40 MPs respectively; at the other, you have the rural eastern districts along the border with Spain, which elect between two and four MPs each.

This vast range means that a rural focussed party will need to win a significantly higher share of the vote than one whose support is concentrated in the big cities. For example, in 2022, the left-wing CDU won 15% of the vote in the rural district of Évora – the second-highest district-level vote share by any party other than the main two – but won none of the constituency’s three seats. Meanwhile, environmentalist PAN won a seat in Lisbon on just 2% of the vote. This compares to a country like Iceland where, despite a similar average district magnitude, the range is much tighter (all elect between 7 and 11 MPs) and the natural ‘threshold’ much more even across the country.So, while there are many good things about Portugal’s List PR system and it works for Portuguese politics, campaigners for equal votes in the UK should remain cautious about adopting it as a template. A bespoke PR system for the UK would need to deliver the same higher levels of fairness for all parts of the country, carefully balancing local accountability and voter choice with accurate representation.

Image credit: Luís Feliciano