SANTIAGO, Chile — Former leftist student leader Gabriel Boric will be under quick pressure from his youthful supporters to fulfill his promises to remake Chile after the millennial politician scored a historic victory in the country’s presidential runoff election.

Boric spent months traversing up and down Chile vowing to bring a youth-led form of inclusive government to attack nagging poverty and inequality that he said are the unacceptable underbelly of a free market model imposed decades ago by the dictatorship of Gen. Augusto Pinochet.

The bold promise paid off. With 56% of the votes, Boric on Sunday handily defeated his opponent, far right lawmaker José Antonio Kast, by more than 10 points and at age 35 was elected Chile’s youngest modern president.

Amid a crush of supporters in downtown Santiago, Boric vaulted atop a metal barricade to reach the stage where he initiated in the indigenous Mapuche language a rousing victory speech to thousands of mostly young people.

“We are a generation that emerged in public life demanding our rights be respected as rights and not treated like consumer goods or a business,” Boric said. “We know there continues to be justice for the rich, and justice for the poor, and we no longer will permit that the poor keep paying the price of Chile’s inequality.”

In his speech, the bearded, bespectacled president-elect highlighted the progressive positions that launched his improbable campaign, including a promise to fight climate change by blocking a proposed mining project in what is the world’s largest copper producing nation.

He also called for an end to Chile’s private pension system — the hallmark of the neoliberal economic model imposed by Pinochet.

It’s an ambitious agenda made more challenging by a gridlocked congress and ideological divisions recalling the ghosts of Chile’s past that came to the fore during the bruising campaign.

Kast, who has a history of defending Chile’s past military dictatorship, finished ahead of Boric by two points in the first round of voting last month. But his attempt to portray his rival as a puppet of his Communist Party allies who would upend Latin America’s most stable, advanced economy fell flat in the head-to-head runoff

Still, in a model of democratic civility that broke from the polarizing rhetoric of the campaign, Kast immediately conceded defeat, tweeting a photo of himself on the phone congratulating his opponent on his “grand triumph.” He then later traveled personally to Boric’s campaign headquarters to meet with his rival.

And outgoing President Sebastian Pinera, a conservative billionaire, held a video conference with Boric to offer his government’s full support during the three-month transition. That will follow a runoff that saw 1.2 million more Chileans cast ballots than in the first round and raise turnout to nearly 56%, the highest since voting stopped being mandatory in 2012.

“It’s impossible not to be impressed by the historic turnout, the willingness of Kast to concede and congratulate his opponent even before final results were in, and the generous words of President Pinera,” said Cynthia Arnson, head of the Latin America program at the Wilson Center in Washington. “Chilean democracy won today, for sure.”

In Santiago’s subway, where a fare hike in 2019 triggered a wave of nationwide protests that exposed the shortcomings of Chile’s free market model, young supporters of Boric waved flags emblazoned with the candidate’s name while jumping and shouting as they headed downtown for his victory speech.

“This is a historic day,” said Boris Soto, a teacher. “We’ve defeated not only fascism, and the right wing, but also fear.”

Boric will become Chile’s youngest modern president when he takes office in March and only the second millennial to lead in Latin America, after El Salvador’s Nayib Bukele. Only one other head of state, Giacomo Simoncini of the city-state San Marino in Europe, is younger.

The new government is likely to be closely watched throughout Latin America, where Chile has long been a harbinger of regional trends.

It was the first country in Latin America to break with U.S. dominance during the Cold War and pursue socialism with the election of Salvador Allende in 1970. It then reversed course a few years later when Pinochet’s coup ushered in a period of right-wing military rule that quickly launched a free market experiment throughout the region.

Boric’s ambitious goal is to introduce a European-style social democracy that would expand economic and political rights to attack nagging inequality without veering toward the authoritarianism embraced by so much of the left in Latin America, from Cuba to Venezuela. It’s a task made more urgent by the coronavirus pandemic, which sped up the reversal of a decade of economic gains.

Boric was able to prevail by expanding beyond his base in the capital, Santiago, and attracting voters in rural areas. For example, in the northern region of Antofagasta, where he finished third in the first round of voting, he trounced Kast by almost 20 points.

Also key to his victory were Chilean women, a key voting bloc who feared that a Kast victory would roll back years of steady gains. Kast, 55, a devout Roman Catholic and father of nine, has a long record of attacking Chile’s LGBTQ community and advocating more restrictive abortion laws. One of his supporters even joked that

Boric, in his victory speech, promised that Chile’s women will be “protagonists” in a government that seeks to “leave behind once and for all the patriarchal inheritance of our society.”