In the weeks leading up to the vote, the Spanish government's strategy was to delegitimize the referendum by disrupting its organization. From a purely logistical point of view, it was a partial success. Several polling centers were closed and ballot boxes were confiscated, forcing people to vote under irregular circumstances, without a valid electoral roll and without any controls to prevent them from voting multiple times. Consequently, the referendum results — in which 90 percent of voters favored independence, with a voter turnout of roughly 40 percent according to the Catalan government — cannot be considered reliable.

But if the Spanish state obtained a partial logistical victory, it came at a high political cost. Though a judge authorized the police crackdown on voters (the Constitutional Court had banned the referendum), it still shocked Catalans and international public opinion. The resulting peaceful disobedience of hundreds of thousands of Catalans gave the independence process an appearance of legitimacy it did not have before. So even though many of the Catalan government's arguments for independence are dubious, Madrid's actions have now given Barcelona additional pretext to unilaterally declare independence.

From the start, Spanish Prime Minister Mariano Rajoy's strategy to deal with the Catalan situation has been controversial. Many opposition parties questioned Madrid's almost exclusive focus on the illegality of the referendum and requested that the government diffuse tensions and weaken the separatist movement by making political gestures like promising fiscal and institutional reforms. But while the Spanish government could have chosen a different strategy to deal with the Catalan crisis, there are still clear constraints limiting its room to maneuver.

Spain's mountainous geography has led to the emergence of strong regional identitiesthat are distrustful of the central government. For the past five centuries, successive Spanish governments have opted for a stick and carrot approach to prevent the country from disintegrating. The 20th century offers clear examples of both: While Francisco Franco's dictatorship from 1939-1975 tried to suppress Spain's regional identities by denying them political and cultural rights, the constitution of 1978 created one of the most decentralized political systems in Europe, giving Spanish regions high degrees of autonomy.

That system was meant to reduce Spain's natural tendency toward fragmentation, but it didn't eliminate it completely, and Spain today is still divided. The current conservative government in Madrid is unlikely to authorize a legal referendum in Catalonia, as it would open the door for other regions — most notably the Basque Country and, to a lesser extent, Galicia — to demand the same. Even a progressive administration would be skeptical of any decisions that could lead to the breakup of the country.

Then there is the issue of the emotional link between Catalonia and Spain, which has deteriorated over the past decade. An economic crisis, rising anti-establishment sentiments, recurrent corruption scandals and controversial political events, such as the Spanish Constitutional Court's decision to block parts of Catalonia's statute of autonomy in 2010, have all damaged the image of the Spanish state in the eyes of many Catalans. The Catalan government, in turn, has made consistent efforts to deepen nationalist and anti-Spanish sentiments in the region. A strong narrative has taken root in the region, presenting the Spanish state as something alien, distant and hostile to Catalonia. As a result, support for Catalonia's independence rose from roughly 20 percent to around 50 percent between 2007 and 2017.

Opinion polls before Oct. 1 suggested that a significant part of Catalan society would welcome institutional reforms to grant Catalonia a greater control of its taxes while keeping the region within Spain. Catalonia represents roughly 20 percent of the Spanish GDP and Madrid would be reluctant to give up substantial amounts of money it uses to run the state and to spend in other regions. But these reforms may prevent the country from breaking, though they are not currently on the table. That's because Madrid and Barcelona have presented their dispute as a zero-sum game in which one of the two parties has to be defeated.

Yesterday's events have only made things worse, because the Catalan government is now one step closer to declaring independence, which could force Madrid to react by suspending Catalonia's autonomy or calling for early regional elections. While either of these options would remove the current Catalan leadership — which Madrid doesn't consider valid — from the equation, they would only lead to additional social unrest and potentially new episodes of violence. Moreover, suspending autonomy or holding early regional elections without first introducing real institutional reforms at the national level would do little to resolve the crisis. Pro-independence sentiments are unlikely to go away anytime soon.

In this context, Rajoy's minority government could become fragile domestically and internationally. So far, two of the three largest opposition parties in Spain have supported Madrid's decision to block the Catalan referendum. But the images of the police cracking down on voters are making it difficult for unionist parties to side with Rajoy's government. The same goes for the European Union, which supported Rajoy before the referendum but chose to remain silent as events unfolded on Oct. 1. Should social unrest in Catalonia grow, the bloc will probably change its view of the crisis as a domestic issue and pressure Madrid to negotiate a compromise. After all, Brussels and many of the bloc's governments are unlikely to tolerate prolonged instability in the fourth largest economy in the eurozone. In fact, on Oct. 2, the EU Commission urged "all relevant players" in the referendum to "move very swiftly from confrontation to dialogue."

Things in Catalonia are likely to get worse before they get better. And even if the Spanish government manages to keep the country together, the crisis will leave long-lasting scars, which will shape Spanish politics for years to come.