The conservative opposition leader Mauricio Macri will be the new president of Argentina, following his narrow victory in Sunday's election over the government-backed candidate Daniel Scioli.
Macri's win marks a major shake up in Argentine politics. It puts a definitive end to 12 years of Kirchnerismo — the last two terms under outgoing President Cristina Fernández de Kirchner and the first headed by her late husband Nestor Kirchner.
Sunday's poll also looks like a warning shot across the bows of several leftist Latin American governments that, like the Kirchners' administrations, are associated with a broad shift to the left that reached its height a decade ago but are now bleeding support in the face of economic downturns and corruption scandals.
"With your vote you have done the impossible, what nobody believed could happen," Macri told the crowd celebrating his victory with 51.4 percent of the vote over Scioli's 48.6 percent. "It was true that we were going to change history. We did it."
Macri's win is rooted in his success in laying the blame on the Kirchner era for chronically high inflation, rising crime, confrontational domestic and international politics, and a series of corruption scandals. Scioli's campaign, meanwhile, focused on fears that the opposition victory would bring economic austerity and currency devaluation.
Macri, who has been the mayor of the capital Buenos Aires for eight years, comes from one of Argentina's most prominent business families and is viewed favourably by international markets. This contrasts sharply with Fernández who regularly alleged that the markets were punishing Argentina, at the same time as her administrations were frequently accused of capriciousness and lack of transparency.
As Macri's supporters celebrated around Buenos Aires on Sunday night the mood was desolate outside Scioli's headquarters in a Buenos Aires hotel as the losing candidate recognized defeat. President Fernández reportedly called Macri immediately to set up a meeting on Tuesday to begin the transition ahead of his inauguration on December 10.
Macri's unbridled optimism on Sunday — as he told his supporters that "Argentina is starting a wonderful new phase" — ignored the many serious obstacles he will face delivering the sweeping change he has promised.
The narrowness of his victory and his lack of a majority in Congress will oblige him to negotiate with the statist Peronist movement, which now passes to the opposition. The party founded by Juan Domingo Perón in the 1940s, together with its legendary machinery, still constitute a major political force to be reckoned with, even though it is currently split into two major currents — Kirchnerismo and orthodox Peronism.
Already there is tension in the air with press reports circulating in the early hours of Monday suggesting Scioli will demand a recount and Macri's camp will denounce dirty election practices by the Peronist machine.
Meanwhile, how President Macri's economic team will deal with the country's many and varied economic problems remains unclear. Early suggestions that he would reduce subsidies, privatize some state-owned companies, devalue the currency, and remove the restrictions on dollars leaving the country were softened substantially as the campaign heated up.
Then there is the thorny problem of the country's debt, and the holdouts held by the so-called "vulture funds" that were not included in the Kirchners' overall renegotiations of Argentina's 2001 debt default. Fernández has refused to comply with a 2012 decision by a judge in New York in favor of the vulture funds' demands for payment in full that also impacted Argentina's ability to raise money to make good on the rest.
Members of Macri's economic team have claimed his market-friendly reputation will put him in a better position to negotiate an end to the stand-off. They have also suggested that they expect the vulture funds to accept some kind of compromise in the name of getting paid something.
It is also not clear what Macri's presidency will do with agreements Fernández made with Russia and China. Some of these are deeply controversial, such as a Chinese satellite space station in Patagonia in the south of the country.
There is much less doubt, meanwhile, over the message the political earthquake in Argentina holds at a regional level.
Macri's most obvious Latin American allies include Colombia's Juan Manuel Santos and Mexico's President Enrique Peña Nieto, who was the first to wish him "success in his administration" in a tweet.
Even before polling day others within the leftist block were already making their lack of enthusiasm for a Macri victory clear. Both Brazil's President Dilma Rousseff and Bolivia's President Evo Morales openly expressed their support for the government-backed candidate. "Daniel is an Argentine friend and a Latin American brother and, above all, a revolutionary of the great homeland," Morales said last week.
Macri himself used his celebration to send a direct message to Venezuela's President Nicolás Maduro.
"We say to our Latin American brothers that we want good relations with all our countries. Argentina has a lot to offer the world. We hope to find an agenda of cooperation," Macri said in his victory speech. Then he hugged Lilian Tintori, the wife of imprisoned Venezuelan opposition leader Leopoldo López who accompanied him on the stage.
"Hope won in Latin America today," Tintori tweeted, alongside a photograph of her celebrating with Macri. "Its next destination is our beloved Venezuela."
Follow Gaston Cavanagh on Twitter: @gastoncavanagh