Just under a year ago, Vox was dismissed as a bunch of extremist oddballs by critics who insisted it would remain in the political wilderness in a country which had long prided itself as having no far-right party.
But on Monday, Spaniards woke up to the reality that with 52 MPs Vox is the third biggest force in the Congress of Deputies, the Spanish lower house of parliament.
This political bombshell has come about because of a combination of global and local factors, not to mention a bit of luck, say commentators.
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Catalonia, Spain’s political running sore, has been the dominating factor.
The jailing of nine Catalan separatist leaders for up to 13 years last month for their roles in a failed independence bid sparked weeks of riots in Barcelona and beyond.
From its inception, Vox has maintained a hard line against Catalan separatism, even mounting its own private prosecution against the nine politicians and civic leaders who were eventually jailed.
Vox advocates the outlawing of secessionist parties and a return to centralised government for Spain, which is Europe’s most devolved nation.
A rising Spanish nationalism, inspired by a reaction against efforts by separatists to split from Spain, has fuelled the Vox revolution like nothing else.
As the streets of Barcelona became a battlefield last month, the acting Socialist government appeared to some unable – or unwilling – to intervene.
Vox, in contrast, urged the government to bring in direct rule once again.
Santiago Abascal, the Vox leader, told me in an interview last year: “After we took a stand on Catalonia, we started to grow.”
With hindsight, this comment seems prophetic.
At the same time as the clashes in Barcelona, Pedro Sanchez, the acting Socialist prime minister, finally overcame a series of legal hurdles so his government could move the remains of the late Spanish dictator General Francisco Franco from a huge mausoleum outside Madrid to be reburied beside his late wife, Carmen Polo in the Spanish capital.
Mr Sanchez claimed Franco’s huge tomb had served to glorify the dictatorship and removing his remains would help heal wounds still festering from the civil war, which ended 80 years ago in 1939.
Instead, critics said, the live televised spectacle of Franco’s exhumation served only as a great advertisement for the dictator.
Mr Abascal was only the politician to publicly condemn the exhumation, saying Spain should look to the future not the past.
Emilia Landaluce, a journalist and author of We Are Not Fascists, a book about the Spanish right, said that “traditional” voters feel let down by the general silence over Franco’s exhumation.
“The voters of the traditional parties like the Popular Party and Ciudadanos felt betrayed that their leaders had not said anything. They were against the exhumation. Only Abascal spoke out.”
On a deeper level, Vox has thrived on a reaction against globalisation among an increasing number of Spaniards, believes Xavier Arbos, a professor of constitutional law at the University of Barcelona.
“Just as happened with Trump in the US and with Brexit in Britain, there are obviously Spaniards who feel isolated by the political system in an era of globalisation.
“They did not feel represented by the mainstream conservative Popular Party and Ciudadanos, so they turned to Vox,” he said.
“Vox have fostered a sense of belonging. You can see they have also crossed classes as they have won seats in upper class areas and more working class areas where the Socialists had been popular.”
Mr Arbos believes Spain has joined other European countries like Italy or France where a right-wing populism has gone mainstream.
Vox party members wear red and gold wristbands with the colours of Spain and the slogan Espana Viva (Spain Lives).
The wristband has become a kind of fashion symbol for right-wingers who identify with Vox’s values of nation, sovereignty and symbols of a certain version of the Spanish way of life like hunting or bullfighting.
And not for nothing did they choose green as the party’s colour – it symbolises life in the countryside – or campo, which many Vox voters hold dear.
After the party made their breakthrough by winning 24 seats at inconclusive general elections in April, the leadership began a process of “normalisation”.
“We did not want people to be afraid of us any more, to see us as the ‘nasty party’,” said a party insider.
“We wanted to be seen as just another political party.”
Analysts believe Vox represents a viewpoint which is not afraid to say what has so far been the politically unpalatable. Its unabashed use of the Spanish flag after years in which the national ensign was shunned appears to be one symbol of this.
More controversially, it has criticised gender laws brought in to protect victims of domestic violence, claiming they are unfairly biased towards women.
“It is the populist rejection of the political correctness of the left,” said Ms Landaluce.