With 99 percent of the vote counted, Bildu increased its representation from 21 to 27 mandates in the 75-seat Basque parliament, giving it the same result as the centrist Basque Nationalist Party (PNV), which has ruled the region for decades.

Polls had predicted a tight race, seeing a narrow victory for Bildu — a coalition which has worked to disassociate itself from ETA, whose bloody struggle for an independent Basque homeland claimed 850 lives before it rejected violence in 2011.

And six years after ETA’s dissolution, EH Bildu has pursued a winning strategy, putting its pro-independence demands on the back burner and focusing strongly on social issues, securing a solid following among young people under 40.

READ ALSO: Does the Basque Country still want independence from Spain?

Despite the results, analysts said the current coalition grouping the PNV and the regional branch of Prime Minister Pedro Sanchez’s Socialist Party, which came third with 12 seats, would likely be returned to power.

“The PNV has won the elections, it came first in terms of votes and drew in terms of seats,” said its leader Andoni Ortuzar, pledging to put together a new coalition.

At Bildu’s headquarters, there were scenes of celebration, with its candidate Pello Otxandiano hailed by cheering, flag-waving supporters.

“This is the best result the separatist left has ever had in its history,” he said to rapturous applause.

“Four years ago, very few people would have imagined that we would be here today with these results. We have taken a huge step forward,” he said.

Ahead of the vote, Pablo Simon, a political scientist from Madrid’s Carlos III University, said even if Bildu won, it wouldn’t have been able to govern “because no party will be willing to make an alliance with it”.

Some 1.8 million people were eligible to vote, casting ballots for the parliament’s 75 lawmakers, with official figures putting turnout at 62.5 percent.

Socialists as kingmaker

Voters said the rise of Bildu had given them more choice.

“Before, the only party looking after Basque interests was the PNV, so everyone voted for them regardless of their political leanings,” social worker Elena Garcia, 40, told AFP, saying the ETA era was now well in the past.

“But now if you are left-wing and more socially minded, you will vote for Bildu.”

With neither party winning an absolute majority of 38 seats, it was clear the Socialists would be cast as kingmaker.

Until now, the PNV has governed the Basque Country in coalition with the Socialists — who have ruled out supporting Bildu, whose leader, Arnaldo Otegi, was convicted of ETA membership but later credited with helping steer the group away from violence.

“Condemning terrorism is (Bildu’s) outstanding debt to Basque society and as long as they do not do that… we will not make any type of deal with them,” the Socialist candidate Eneko Andueza told public radio.

Throughout the campaign, the issue hardly came up until earlier this week, when Otxandiano sparked anger when he failed to call ETA a “terrorist organisation”, referring to it only as an “armed group”.

READ ALSO: Why the Basque Country is Spain’s industrial powerhouse

A wealthy region

With 2.2 million residents, the Basque Country has the second highest regional income per capita in Spain, after Madrid, which averages around 36,000 euros ($38,400).

Its economy accounts for 5.9 percent of Spain’s gross domestic product, ranking fifth of Spain’s 17 regions, CaixaBank research figures indicate.

It is also the region with the lowest unemployment figure in Spain at 7.9 percent, according to Basque government figures.

The father of Basque nationalism was Sabino Arana, who set up the PNV in 1895.

His ultra-Catholic, anti-Spanish ideology grew out of his vehement opposition to the thousands of Spaniards flocking to the area as a result of the industrial revolution.

ETA emerged in 1959 out of a split within the PNV’s youth movement, who were angered by what they saw as the party’s inability to stand up to Francisco Franco’s dictatorship.

In its first recorded act of bloodshed, ETA militants shot dead a policeman on June 7, 1968 in the city of Villabona, according to Spanish interior ministry documents.