Eager to maintain his leadership, Prime Minister Sanchez of Spain is nearing a deal that would tie him in a coalition with Catalan separatist parties and would risk breaking up the country as we know it. 

Mr. Sanchez’s candidate, Francina Armengol, was named president of the parliament Thursday, following a deal the ruling Spain Socialist Workers Party made with two separatist groups, Junts and Esquerra Republicana. Since coming in second to the conservative Popular party in last month’s elections, the Socialists have been trying to negotiate with several parties to create an absolute majority in parliament. 

In exchange for its support for re-election, Junts is asking for seemingly non-negotiable terms, including a referendum for independence from Spain of the Catalan region. Junts also demanded amnesty for its exiled president, Carles Puigdemont, and other party members, who, in 2017, conducted an illegal referendum on independence. Mr. Puigdemont has been self-exiled at Brussels for the last six years.

Mr. Sanchez has long considered the independence plebiscites to be unconstitutional. Now, his would-be separatist partners are likely to push for them in exchange for support for re-election, a professor of Communication and International Politics at the European University of Madrid, José María Peredo Pombo, tells the Sun.

The deal on Thursday indicates that negotiations leading to a ruling parliamentary coalition led by Mr. Sanchez’s Socialist party are advancing, Mr. Peredo Pombo says. Among the would-be partners are nationalists parties such as EH Bildu, a political wing of the Basque separatist group Euskadi Ta Askatasuna, and Junts. A coalition bloc would secure Mr. Sanchez’s hold on the premiership.

The negotiations for creating a coalition could still collapse. Junts president, Mr. Puigdemont, for one, assured his voters that the party’s support of the Socialists on Thursday was only to assure Ms. Armengol gets the parliamentary presidency and does not necessarily mean Junts would support Mr. Sanchez’s premiership. 

That stance is confusing, a Bard College professor specializing in Spanish politics, Omar Encarnación, tells the Sun. “In a parliamentary system,” he adds, “whoever controls the parliament also controls the presidency of the government.”

Mr. Encarnación says any agreement between the socialists and the separatists that includes a referendum would collapse since the Constitutional Court declared it unconstitutional. A compromise can be reached on an amnesty deal, he adds, “but Sanchez cannot be seen as giving everything away to the separatists,” as it “will weaken his mandate.” 

Following the election on July 23, Junts became a potential kingmaker, as its seven seats could be the decisive factor on which camp would secure a parliamentary majority. The party’s vice president, Josep Rius, told Reuters that its demands were clear: “An agreed, binding and verified referendum on independence.”

Granting an independence vote could raise concerns among the Spanish people, echoing their anger toward the government when Mr. Sanchez pardoned nine Catalan separatist leaders who were part of the 2017 illegal referendum.

The conservative party that won the largest number of votes, however, seems to reject any coalition with the separatists. “It would be a huge mistake for separatists to govern Spain,” the head of the Popular Party, Alberto Núñez Feijóo, told reporters last month at Santiago de Compostela.

For now, Mr. Núñez Feijóo is struggling to secure a parliamentary majority, while the left-leaning parties are making advances that could strengthen Catalans that clamor for independence from Spain.