Los Remedios doesn’t have the feel of a political frontline. Rowers glide along the green waters of the Guadalquivir, a huge Christmas tree sits beneath a warm December sky and the nearby churrería is already bedecked with artificial poinsettias.

Beneath the Spanish flags that stripe many balconies, residents and the odd labrador stroll down citrus-tree-lined boulevards, past designer shops and a tobacconist’s with bottles of Moët in its window.

Oranges, however, aren’t the only things ripening in this comfortable Seville neighbourhood, or beyond. In last Sunday’s Andalucían regional elections, the tiny Vox party became the first far-right grouping to win seats since Spain’s return to democracy following the death of General Franco in 1975.

The 12 seats it picked up in Andalucía’s 109-seat parliament exceeded all expectations and could see the socialist PSOE party lose control of the heartland it has governed since 1982. But more importantly, they ended four decades of Spanish exceptionalism and showed that the country’s fabled immunity to far-right politics had finally given out.

The middle and upper-middle class voters of Los Remedios – many of whom are older people – have long been loyal to the conservative People’s party (PP).

In the last Andalucían election three years ago, the PP took 61% of the vote in the barrio, with Vox limping far behind on 3.2%. On Sunday, the PP’s share of the vote in Los Remedios was down to 37.3%; Vox’s was up to 24.7%.

Until this week, Vox were a bunch of fringe populists, best known for unsubtle gestures such as unfurling a giant Spanish flag on the Rock of Gibraltar. A widely mocked video released in early November showed Vox leader Santiago Abascal leading a posse on horseback and the party boasting of a “reconquest” of Spain that would begin in Andalucía. One month on, the video, like the party itself, no longer seems quite as absurd as it once did.

Facebook Twitter Pinterest Vox leader Santiago Abascal has boasted of leading a ‘reconquest’ of Spain. Photograph: Luca Piergiovanni/EPA

David Duke, former “grand wizard” of the Ku Klux Klan, has been thrilled by the prospect of Vox’s reconquista, as has Marine Le Pen, who tweeted her congratulations to “our Vox friends, who have achieved a really significant result in Spain for a young and dynamic movement”.

Vox’s Andalucían leader, Francisco Serrano, may have been lambasted for tweeting about women who are too unattractive to be gang-raped, about “psychopathic feminazis”, about the threat immigrants pose to European identity, and about his pride in being branded sexist. But to the Vox faithful, Abascal, Serrano and others are speaking directly to, and for, them at a time when the Spanish right is fragmenting and the PP, the centre-right Ciudadanos party and Vox are desperately competing for votes.

A Vox supporter pushing her two children down Los Remedios’s main shopping street offered her own explanation for the party’s sudden rise. “I voted Vox because the PP has stolen a lot and changed nothing,” said the woman, who didn’t want to give her name for fear of damaging her business.

Like many of those who voted Vox, she had abandoned the PP because of the series of corruption scandals that tarnished the party in recent years before eventually bringing down Mariano Rajoy’s conservative government seven months ago.

And then there was the issue that forms one of the main planks of the Vox platform: immigration. “Vox got 12 seats with no publicity because it’s defending Spain and its people,” she said. “Yes, we should look after immigrants, but we should look after our own people first.”

José María Cañizares, chair of the local residents’ association, believes that the PP’s long, slow fall from grace has done more for Vox than immigration. Besides the sub-Saharan African men begging or selling tissues at traffic lights, he said, immigration had not caused many problems in the area.

“For a while now, people in the association have been telling me that they feel let down by the PP; by all these rogues and crooks. They feel disenchanted; they feel that these people don’t represent them.”

Facebook Twitter Pinterest Vox supporters celebrate on election night last week. Photograph: Gogo Lobato/AP

But, he added, the PSOE’s Andalucían leader, Susana Díaz, must accept some of the responsibility for the rise of Vox. “Most people didn’t know about Vox round here,” said Cañizares. “But a week before the elections, Díaz started banging on about “Vox! Vox! Vox!’. That made people start wondering who Vox were. The best advertising Vox had was Díaz talking about Vox.”

Roberto Ruíz, who was smoking an early morning cigarette on a bench, voted PP again last Sunday – but not enthusiastically. When asked about Vox, the 75-year-old pointed up at the balconies and proffered another theory. “Catalonia’s trying to split from Spain, which is why you can see all these flags,” he said. “A lot of the blame for what’s happened is on Rajoy. He was very late in applying article 155 [to assume direct control of Catalonia late last year] and his government let itself be tricked by the Catalans.”

Most political analysts see the Catalan crisis and the issue of immigration – a record 53,500 migrants and refugees arrived on the southern shores of Spain this year – as key components of Vox’s nationalistic narrative.

But they are not the only factors that explain the breakthrough of a party that calls for the repeal of Spain’s gender-violence legislation, the “abolition of subsidised radical feminist organisations”, an end to public funding of “non-health-based surgery” (gender changes, abortion), and a law to protect bullfighting.

Berta Barbet, editor of the political analysis website Politikon and a researcher at the Autonomous University of Barcelona, counselled against overestimating the part that Catalonia had played in all this. “While the Catalan question is relevant, you can’t understand the phenomenon without looking at Vox’s two big issues: immigration and anti-feminism,” she said.

“I don’t think that the rise of Vox now is down to the fact that there’s suddenly a higher number of people with racist, xenophobic or anti-feminist views. That was already there; it just hadn’t been articulated politically until now.”

Ignacio Jurado, a senior lecturer in politics at the University of York, also saw evidence of an older culture war in Vox’s success. “Maybe the question should be: why didn’t we have an extreme-right party until now?” he said. “The conditions for a small, far-right party were already there. In Spain, we’ve been at the forefront of feminism and gay rights, and this has provoked a conservative reaction like the ones we’ve seen in some other European countries.

Facebook Twitter Pinterest With the numbers of people seeking to enter Spain on the rise, rightwing parties have sought to exploit the issue of immigration. Photograph: Carlos Barba/EPA

“We also have immigration levels that are comparable to other European countries – and immigration always generates a kind of tension; you get nationalist, cultural reactions that use the issue of immigration as a way to express themselves.”

When the PP was in power, argued Barbet, it managed to “keep a lid on things” by welcoming the entire spectrum of the Spanish right – from centrists to nostalgic fascists – under its wide roof. “But the PP’s crisis made it less attractive and people saw that there were alternatives,” she said.

While it remains to be seen whether Vox can build on its momentum – whether it will find a place in the next Andalucían regional government, how it will do in May’s municipal, regional and European elections, not to mention the next general election – its presence in mainstream Spanish politics is now undeniable.

So, too, is its impact on its rightwing rivals. “The Spanish right is super-competitive at the moment: there are three parties and there’s not enough cake to go round,” said Jurado. Sunday’s results, he added, would only push the PP even further to the right: “That’s one of the effects that far-right parties have – they may not have many seats but they can still drive the agenda.”

Vox’s victory came four days before Spain celebrated the 40th anniversary of the constitution that ushered in its modern democracy and marked the definitive end of almost four decades of dictatorship.

What was unthinkable even a year ago has materialised, and those to whom the party has given a voice are relieved, exultant, and already a little defensive.

“People say Vox are homophobic and racist and anti-feminist because it’s the only way they have to attack them,” said the woman with the pushchair. “I don’t think Vox are that radical … They just want to make things fairer.”