Spain is determined to prevent a Catalonian referendum on independence, even though its tough attitude toward Catalan leaders has probably only increased enthusiasm for a measure with questionable support.

A new round in a long game of chicken began earlier this month, after Catalonia’s president, Carles Puigdemont, announced an independence referendum on Oct. 1. Spain’s culture, sport and education minister, Íñigo Méndez de Vigo, vowed: “What I can say is what will not happen on Oct. 1 — an illegal referendum that goes against the Constitution.”

After Catalonia’s government staged a nonbinding independence vote in 2014, Spain charged the autonomous region’s leader at the time, Artur Mas, with the crimes of disobedience and breach of trust. In March, a court fined Mr. Mas the equivalent of $39,000 and banned him from holding public office for two years. The trial only succeeded in galvanizing Catalan separatists, as hundreds of thousands took to the streets in September to demand that their politicians push ahead on independence.But while independence was approved in the 2014 ballot measure, less than half the electorate took part, and many Catalans see clear advantages in remaining a part of Spain, such as membership in the European Union.

Spain might suppress secessionist impulses more successfully by putting its own house in order. Political gridlock and two inconclusive elections left Spain effectively without a national government for 10 months last year, and while the government, reeling from a corruption scandal, survived a no-confidence vote last week, the effort showed that political divisions continue to roil Spain.

A more capable central government could head off independence fervor by giving the region a better economic return. Catalonia contributes nearly a fifth of Spain’s gross domestic product, yet the region receives just 9.5 percent of Spain’s national budget. Negotiating in good faith with Catalan leaders to find a political solution, rather than relying on the judiciary’s restrictive interpretation of the Constitution to punish Catalan efforts for greater autonomy, would also help.

The best outcome for Spain would be to permit the referendum, and for Catalan voters to reject independence — as voters in Quebec and Scotland have done. Otherwise, Madrid’s intransigence will only inflame Catalan frustrations. [….]