Hype around the Dutch, French, and German elections this year has overshadowed what is likely an even larger threat to European integration. For years, the government in Spain’s Catalonia region has been pushing for a Scottish-style vote on independence. But unlike the what happened in the UK, the Spanish government has been pulling out all the stops to prevent such a vote from happening at all. Nevertheless, Catalonia’s government has defied Madrid by promising a referendum to its people this year. With polls showing public opinion evenly split, there is a real chance for Catalan independence in the coming months and years, possibly triggering the region’s exit from the European Union (EU).

The build-up

Catalonia is one of Spain’s most distinct regions. With its own language, culture and traditions, it is in many ways a country within a country. Centuries of Spanish rule have not stopped Catalans from asserting their identity, from a push for autonomy within the Spanish Republic of the 1930s, to underground resistance against the Franco regime (see here for a brief primer).

Today, Catalonia boasts the most dynamic economy in Spain, punching above its weight on a number of key indicators like foreign trade and attracting investment. As a result, it supports other, poorer parts of Spain financially—a system many Catalans feel is unfair. For example, a majority of the region’s highways are tolled, while its residents must pay for the construction of toll-free highways in other regions.

In 2006, Catalonia’s regional government proposed the Statute of Autonomy of Catalonia to lawmakers in Madrid as a means of holding more power over their finances and identity. After multiple amendments and a referendum, the Statute passed. Then-opposition leader Mariano Rajoy’s People’s Party (PP) challenged the agreement in Spain’s Constitutional Court, however. In 2010, the Court stripped the Statute of many of its most important clauses, effectively defeating Catalonia’s ambitions for further autonomy within a federal Spain. Many see this moment as the spark leading to the current conflict.

The road to independence

Following regional elections in 2012 Catalonia’s parliament responded to widespread anger at Madrid’s resistance to further autonomy by resolving to hold a referendum on independence before the next election. This was met with even more resistance from Rajoy (who had just become prime minister).

The federal government’s intransigence only served to fan the flames of the independence movement. Despite a court ruling preventing Catalonia from holding a referendum, Catalan President Artur Mas defied Madrid by holding a non-binding “consultation” on independence in 2014, manned not by civil servants but by volunteers. Fewer than half of eligible voters participated, but the result was overwhelmingly in favour of independence.

The consultation was followed by fresh regional elections in 2015, presented as an indirect referendum on independence. Mas’ coalition won a majority of seats, but fell short of a majority of votes. As a result, the regional government opted to declare the initiation of Catalonia’s independence process, followed by the creation of a foreign ministry to gain international recognition. For holding the consultation, Mas was banned from holding public office, leading to his replacement by long-standing independence advocate Carles Puigdemont.

In a new year’s address, Puigdemont announced his government’s goal of offering a binding referendum on independence in 2017 (likely in September), regardless of reactions from the federal government. Once more, Madrid denounced the move, going as far as (indirectly) threatening the use of an emergency clause in the Spanish constitution allowing the government to intervene directly in a region’s administration.

If the vote goes ahead, it is possible that a majority of Catalans chose independence. Polls are showing an even split, and continued intransigence by the Spanish government may only embolden the independence movement.

What does an independent Catalonia mean for the EU?

The ramifications of Catalan independence would reach far beyond Spain’s borders. Despite Catalonia’s best efforts to ensure continued EU membership following a vote to secede, Brussels has made clear on several occasions that to leave an EU member state means leaving the EU. Where Brexit represents the first time the EU has contracted after decades of expansion, Catalan independence would mark the first time the eurozone has shrunk, striking the European project at its heart.

So, is Catalan independence the next Brexit? A few important events need to occur first, like a successful referendum without Spanish intervention. Nevertheless, an independent Catalan state may be declared before the end of 2017, delivering a huge blow to an EU which thought the worst was behind it.