There is hope here in Catalonia that the new Spanish prime minister, Pedro Sánchez, will be more conciliatory than the last. But he mustn’t make the same mistake as his predecessor, I argue in an op-ed for the Netherlands’ NRC newspaper.

Mariano Rajoy denied the Catalans a referendum on independence and radicalized the region’s autonomy movement. Whereas only one in five Catalans wanted to secede from Spain when he took office, now 40 to 50 percent do.

Similarly, in the Basque Country, only one in five want to break away. But many more want a referendum. The Basques, whose culture and language predate Spain’s, believe they have a right to self-determination.

Sánchez, so far, disagrees. But he has shown magnanimity toward the Catalans, lifting spending controls on the regional government and raising the possibility of constitutional reform. Sánchez shouldn’t fear a federal Spain, I write — and he has no time to lose.

His Socialist government has a majority of four. Right-wing parties oppose more autonomy for the Basque Country and Catalonia. The liberal Citizens, who take the hardest line, are the biggest party in the polls. If Sánchez wants to make his mark, he must do so before elections in 2020.