Spain weighs electoral reform to expand Congress

The proposed electoral reform would expand the Congress to 400 seats, the maximum allowed by the Constitution, and would have to choose between deepening the majoritarian bias or introducing a compensatory nationwide constituency. The outcome would be very different: fewer national kingmaker parties in the first case, more fragmentation in the second.

Spain's electoral system is not purely proportional, and never has been. The Constitution requires the vote to be proportional, but the law that implements it does so with a bias favouring the two major parties. The key lies in the provincial constituency: in large and medium-sized provinces the allocation is close to proportionality, while in small ones the system works almost like a majoritarian one. Since there are many small provinces, the final result tilts towards parties with more vote spread across the country.

## From the UCD to imperfect two-party rule

The original design sought to allow a party with around **35%** of the national vote to govern alone with occasional support. And it worked. For decades, the system favoured an imperfect two-party system: first **UCD** and **PSOE**, then **PP** and **PSOE**. The third and fourth national parties are the most penalised, because above **20%** of the vote there is already overrepresentation and below that threshold the system does not allocate seats proportionally.

The most extreme point of that model came in **2011**, when **PP** and **PSOE** together won **90%** of the seats in Congress. The real barrier to a solid parliamentary group was around **15%** of the national vote, a very high bar. The kingmaker parties that existed were not national, but nationalist or regionalist, favoured by being dominant in specific constituencies.

## The 2011 shift and the bloc model

From **2011** onwards the landscape changes. Four strong national parties emerge, each above **15%** of the vote: **PP**, **PSOE**, **Ciudadanos** or **VOX**, and **Podemos** or **Sumar**. The culmination of that process came in **2019**, with the first coalition in the national government: **PSOE** and **Podemos**, later replaced by **Sumar**.

A bloc model emerged. Each bloc has two parties and there is no strong national centrist party acting as kingmaker. **Ciudadanos** tried and disappeared: it struck a deal with **PSOE** in Congress without a sufficient majority and later agreed regional governments with **PP**. In **2023**, the kingmaker role was taken by **Junts**.

## The two models on the table

If the polls are right and the **PP** and **VOX** bloc wins a broad absolute majority in **2026**, it would have room to reform the electoral law. There are two paths, both keeping the mandatory **2** seats per province and without being able to introduce a purely majoritarian system, because the Constitution forbids it.

The first deepens the majoritarian bias: raising the chamber to **400** seats, the maximum allowed, and applying in each province a mixed model with half proportional and the other half single-member majoritarian. It would favour two large coalitions, **PP** and **VOX** against **PSOE** and a broad front. The second keeps the provincial constituency, also with **400** seats, and creates a nationwide constituency to compensate smaller national parties. It favours large national parties that could replace **PP** and **PSOE**, but brings more fragmentation and more government instability.

## The 5% threshold and open lists

The European Parliament approved a rule requiring each national parliament to set the entry threshold at **5%**. In the Spanish Congress it is **3%** in each provincial constituency, and it has never been applied. If applied per constituency, it would hurt small national parties and some nationalist or regionalist ones. If applied nationwide, it would force nationalist parties to form large coalitions, as happens in elections to the European Parliament.

Another piece would be unlocking the lists and allowing open lists in the proportional segments. The effect would be the end of party discipline as it works today. The D'Hondt law, a mathematical formula, carries an accusation that does not belong to it: the lack of proportionality comes mainly from the size of the provincial constituency, not from the method of allocating remaining seats.

If nothing is reformed, the cycle that began in **1978** will keep repeating itself: an imperfect two-party system with **PP** and **PSOE** dominating national politics. Any change in this area affects political rights and the functioning of institutions, so it should be checked against official sources and legal advice before being taken for granted.