Though it is nonbinding, the vote will be a critical point in a debate that stretches back to the 18th century, when Spain first took control of the northeastern corner of the Iberian Peninsula. Albert Gea / Reuters

The pro-independence flag, known as the Estelada, formed by placards at a demonstration in February. Albert Gea / Reuters

At a pro-independence celebration in Barcelona, Spain, the crowd waves the Catalonian separatist flag, Oct. 19, 2014. On Nov. 9, 2014, Catalonians will vote in a nonbinding poll on the region’s independence from Spain. Albert Gea / Reuters

“Nov. 9 will be another landmark in the continuing series of events in which citizens express themselves freely,” Andreu Mas-Colell, Catalonia’s finance minister, told U.K. newspaper The Daily Telegraph on Tuesday. “It's a celebration of democracy — although not an expression of democracy as we would have liked.”

But nationalists believe a 35 to 40 percent turnout, coupled with a resounding victory for the independence campaign, will send a robust message to Rajoy regarding Catalonia’s desire to chart its own course.

Organizers say about 40,000 volunteers will staff polling stations across Catalonia, although turnout is not expected to be high. Up to 65 percent of those eligible to vote, including a large majority of pro-Spanish Catalans, are likely to abstain from the process.

“In its quest to avoid any discussion about Spanish unity, the Spanish government has [obstructed our] basic rights to freedom of speech and opinion.”

“We hope this vote will show a very large section of the Catalan people believe in democracy as the only means of solving political conflicts,” said Ricard Gené, a spokesman for the pro-independence campaign group Catalan National Assembly.

But this weekend’s proceedings, set to go ahead despite Spanish judicial efforts to stop it , represents a high point in the campaign by Catalan separatists to demonstrate public support for secession.

On Sunday as many as 2 million Catalans are expected to vote on the question of independence from Madrid . Originally billed as a referendum, the vote was downgraded to a “consultation” after a Spanish court ruled that a referendum on the issue would be unconstitutional. The result, therefore, will not be legally binding. The central government in Madrid, led by Mariano Rajoy’s right-wing Partido Popular, has consistently blocked attempts by Catalonia’s regional parliament to stage an official independence vote, such as the one held in Scotland in September.

BARCELONA, Spain — The ruins dating to the 1714 siege of Barcelona that ended Catalonia’s long-standing independence from Castilian Spain are preserved in downtown Barcelona in the striking glass and cast iron structure of the El Born Cultural Center, opened last year. Three centuries on, many in Catalonia — a prosperous region in the northeastern corner of the Iberian Peninsula — are seeking to reverse that defeat.

Adiós, Spain?

Nationalism has long been a major force in Catalan politics. Barcelona was at the center of anti-fascist resistance during the Spanish civil war in the late 1930s. But the origins of the current crisis are more recent.

After the fall of Francisco Franco’s regime in the mid-1970s, Spain adopted a subfederal system of government, with Catalonia as one of its 17 autonomous communities.

For years, most Catalans were relatively content as a distinct group, with limited powers of self-rule, in a broader Spanish union. But over the last decade, support for independence has risen dramatically, from about 15 percent in 2005 to upward of 45 percent today.

The main catalyst for this shift was the decision of the Spanish constitutional court in 2010 to strike down key passages of the Catalan Statue of Autonomy, a document asserting the sovereignty of the Catalan people.

Since then, many Catalans who would once have settled for enhanced devolution within Spain have become convinced that only full independence will deliver the powers they want.

Observers cite Madrid’s refusal to explore alternative constitutional models as a key driver of Catalan nationalism.

“The Spanish government’s view is that the constitution says Spain is one nation," said Kathryn Crameri, author of “Goodbye, Spain? The Question of Independence for Catalonia.” “Therefore nothing can be allowed to rival Spain as the nation. This means there is very little room for political compromise.”

According to Crameri, Madrid’s unyielding approach to Catalonia reflects its fear that far-reaching constitutional reform could lead to Spain’s disintegration as a nation-state.

“Within Catalonia there are people who would still like some form of asymmetrical federalism. But that’s very difficult because the Andalucians would then start asking why they weren’t getting more powers and then the Valencians. So there’s no obvious solution [for Madrid].”

Assuming Sunday’s ballot delivers a “yes” on independence, nationalists are split about how best to proceed.

Radical parties, such as the Republican Left of Catalonia (ERC), want to call fresh regional elections and then — if those elections return a nationalist majority — move toward a unilateral declaration of independence at some point next year.

But more conservative voices, including that of Catalonia’s centrist President Artur Mas, prefer to redouble their efforts to secure a legally binding referendum. Mas has the power to call new elections but is reluctant to do so because his ruling party, Convergencia, is losing ground to ERC and its popular leader, Oriol Junqueras.

“Junqueras is popular for two reasons,” said Laura Pous Trull, a Catalan journalist. “First, because he is the president of ERC, the party that has traditionally advocated independence. Therefore, some ‘yes’ supporters trust him more than Convergencia, which has only embraced independence quite recently.

“And second, he has a very human image. He is seen by many voters as one of us. He is very calm, tries to engage and talk to people and presents his arguments in a very clear way.”

The prospect of ERC’s taking power in Catalonia will worry politicians in Madrid, who have been managing the demands of moderate Catalan nationalists since the early 1980s. Junqueras’ softly spoken radicalism could be the spur that finally brings Catalonia’s fraught relationship with Spain to a head.

“Madrid is more afraid of ERC than it is of Convergencia,” explained Catalan broadcaster Oscar Palau. “They still think Convergencia will [refrain from doing] anything illegal. But if Junqueras is president, he has always said he will declare independence immediately.”

Sunday’s “consultation” will not have any immediate bearing on Catalonia’s constitutional status. The Catalan “yes” movement will almost certainly have to stage a second, more decisive poll if they are going secure a legitimate mandate for independence. But it has one substantial strategic advantage: the intransigence of the Rajoy government in the face of growing popular enthusiasm among Catalans for a separate state.