BUENOS AIRES — People are flooding the streets of Buenos Aires with pans and flags, celebrating what they claim to be a new era in Argentina’s politics. Argentinians wave national flags at the obelisk in the center of the capital. Drivers honk their horns through the city as they hear over the radio that the change they have been waiting for has finally arrived. 

In a historic triumph, the libertarian candidate Javier Milei won the presidential elections in Argentina with 55.7 percent of the votes, defeating the left-wing candidate, Sergio Massa, by almost 12 points. “We are the government,” “Yes we can, yes we can,” “Goodbye thieves,” and “the caste is scared” are some of the things Mr. Milei’s supporters are chanting at his campaign headquarters at the Hotel Libertador at Buenos Aires. 

After 40 years, the young people have taken matters into their own hands, 27-year-old Argentinian Emiliano Rojas tells the Sun. “We got tired of being abused, robbed, unemployed, and so on,” Mr. Rojas says. “They can steal everything from us except the ideas of freedom.”

Cordoba Avenue, where the headquarters are situated, is crowded with Mr. Milei’s supporters waving yellow flags that say “Milei Presidente.” Rock music is getting louder by the minute inside and outside the venue, commemorating the years of the candidate’s youth, when he used to sing in a rock and roll band before starting his career in economics. 

People dressed up as a lion, Mr. Milei’s official animal, jump on top of cars. Others are wearing shirts and hats with Mr Milei’s face on them. The beer on site is being sold for one American dollar in representation of the libertarian’s main campaign goal — dollarizing the economy. “We have to start getting used to it,” the seller says as he goes into the cheering crowd. 

“Today the reconstruction of Argentina begins. It is a historic night,” Mr. Milei said at the beginning of his 17-minute speech. “I want a government that fulfills its commitments, that respects private property and free trade. Enough of the impoverishing caste model.” 

Mr. Milei is often compared to other disruptive figures in the Americas, such as President Trump and Brazil’s Jair Bolsonaro, due to his intentions to restrict abortions and allow the free carrying of guns. “The whole world was watching! I am very proud of you. You will turn your Country around and truly Make Argentina Great Again!” Mr. Trump wrote on his Truth Social platform.

Mr. Milei won in 21 out of 23 provinces, particularly dominating Cordoba and Mendoza. His party, La Libertad Avanza, also prevailed in the northern and southern provinces of the country, breaking the long-lasting left-wing hegemony in those regions. Mr. Massa only triumphed in Santiago del Estero, Buenos Aires province, and Formosa. 

Mr. Massa recognized his defeat around 8 p.m. local time, an hour before official results were announced. “Today confirms that Argentina has a transparent and solid democratic system, which always respects the results,” Mr. Massa said at the beginning of his speech.

“From tomorrow, the responsibility of providing certainty falls on Milei,” he added while confirming he had already called his opponent to congratulate him. Mr. Massa is Argentina’s minister of economy and will leave the country with an annual inflation rate of 142 percent. 

Despite Mr. Massa’s speech promoting a democratic and peaceful transition, election day didn’t come without its difficulties. From the early hours of the day, voters have been sharing through social media videos of Mr. Milei’s ballots with the wrong date on them or torn on the sides. Others claimed someone had soiled a pile of Mr. Milei’s ballots. Members of La Campora also waited for voters outside poll centers and threatened them into telling them they would vote for Mr. Massa.

Mr. Milei will become the next president of Argentina on Sunday, December 10 — which coincides with the 40-year anniversary of Argentina’s return to democracy. Radical Raul Alfonsin assumed the presidency that day in 1983. Mr. Milei has until that day to form a government for the next four years. 

It is expected he will call his new right-wing allies for this: former president Mauricio Macri and his rival during the general elections, Patricia Bullrich. “The majority of Argentines today expressed themselves forcefully, choosing change and rejecting continuity,” Mr. Macri tweeted Sunday night. “There is no doubt that an era begins today. That gives us hope.”