correction

An earlier version of this article misstated Keiko Fujimori's age. She's 46, not 45. The article has been corrected.

LIMA, Peru — Left-wing teachers union leader Pedro Castillo has claimed victory over right-wing former congresswoman Keiko Fujimori in Peru’s closely fought presidential election. But Fujimori has not conceded, and neither election officials nor pollsters or media outlets have declared a result.

Castillo held a lead of 70,000 votes — less than half a percentage point — with 99.99 percent of the ballots in Sunday’s runoff election counted. About 200,000 contested votes are to be reviewed by an electoral tribunal in the coming days.

“This victory is not mine nor of Free Peru” — his party — “but of the people, who have resisted and fought for centuries to achieve a true and honest option for change,” Castillo said in a Facebook post late Tuesday.

Fujimori’s supporters, meanwhile, picketed the offices of the national electoral authority as their candidate made unsubstantiated claims of electoral fraud. Fujimori cited a handful of social media posts of supposed irregularities; she’s launching a legal offensive to contest votes from a range of areas that favored Castillo.

Her lawyers are seeking to nullify the votes, most of them from Andean regions, using a little-known section of Peru’s election law that allows for nullification when fraud, bribery or voter intimidation is proved. The move will delay any official declaration of results.

International observers registered no significant problems with Sunday’s runoff election. Rubén Ramírez, head of a delegation from the Organization of American States, praised the authority for its handling of the “transparent” process and said his team had been made aware of only “isolated” irregularities.

Fujimori has been charged with laundering $17 million and obstructing justice. In an unexpected twist, prosecutors Thursday lodged a request for her arrest, alleging she had “systematically” violated her bail conditions by contacting witnesses. They had previously managed to put her in pretrial detention for 15 months, until an appeals court ruled in April 2020 that the measure was excessive. A hearing has yet to be scheduled.

The choice between Castillo, a rural schoolteacher running with a Marxist-Leninist party, and Fujimori, the daughter of jailed former strongman Alberto Fujimori, offered voters no middle ground. Critics warned that no matter the outcome, the country’s fragile democracy is under threat.

In the days leading up to the vote, Fujimori overcame a 20-point deficit in the polls and a looming corruption trial to draw level with Castillo. She was aided by the first-time candidate’s erratic campaign, which zigzagged between threats to nationalize large chunks of the economy and promises to respect property rights.

For weeks, Castillo, 51, delayed revealing even whether he had a policy team, claiming that he did not want its members to be “stigmatized” and calling expert advisers a “corrupt” political tradition.

Fujimori, 46, rolled out a fearmongering advertising offensive featuring Venezuelan refugees and stoking worry about economic ruin, “communism” and “terrorism.”

The scare tactics received a boost from the reemergence of remnants of Shining Path, the Maoist rebels who wrought havoc in this Andean nation in the 1980s and ’90s. The group is accused of massacring 16 people in a remote valley last month, the worst atrocity in more than a decade.

Castillo reached the runoff with 19 percent to Fujimori’s 13 percent in April’s crowded first round. Allowing for those who spoiled their ballots, left them blank or did not vote, the two actually received the support of just 11 percent and 7 percent of the electorate, respectively.

The election between the two deeply unpopular candidates follows five years of political turmoil caused largely by Fujimori’s Popular Force party helping to oust two presidents. The country is reeling from the coronavirus pandemic; officials here have reported the world’s highest death toll per capita.

Fujimori promised to crack down on crime. She offered a list of populist economic proposals, including handing out a portion of the income from Peru’s corporate mining sector directly to individual citizens.

She also promised to pardon her 82-year-old father. Alberto Fujimori, president of Peru from 1990 to 2000, won broad support here for presiding over the military defeat of Shining Path, but he is now serving a 25-year sentence for the extrajudicial killings of suspected subversives. A pardon would also shut down two pending trials for more killings and the alleged forced sterilization of thousands of mainly poor, Indigenous women in the Andes and the Amazon.

In Keiko Fujimori’s own trial, prosecutors are demanding a 31-year sentence; she had to get special dispensation from a judge to campaign outside of Lima. If she wins, her trial will be postponed until she steps down in 2026.

“I ask for forgiveness from each and every one of you who may have felt affected or let down by us at some point,” Fujimori said last week. She repeated promises that should she win, she would respect judicial independence and step down when her term ends. “I do so with humility, without any reservation, because I know very well that there exist many doubts about my candidacy.”

But Antonio Maldonado, who led the team of prosecutors that extradited Alberto Fujimori from Chile in 2007, dismissed her pledges as “ritual, symbolic promises that lack sincerity and will not be kept.” He warned that any pardon for the former president would be a “grave wound to the rule of law.”

“If she is elected, she will clearly destroy all the advances that Peru has made in the anticorruption fight,” Maldonado said.

Yet most Peruvians are equally skeptical of Castillo. Although he sought to distance himself from his original campaign manifesto, it cites Lenin warning that the media can never be free under the “yoke of capital” and refers to Venezuela as a country that nationalized its oil industry.

The screed was written by former regional governor Vladimir Cerrón, a Cuban-trained surgeon who chose the little-known Castillo to replace him on the presidential ticket after he was barred from running by a corruption conviction. Cerrón faces several more corruption investigations. Many voters think he would be the power behind the throne.

“Let’s recover the riches of our country to distribute them fairly to our children,” Castillo, who teaches in a village school in the northern Cajamarca region, said as he closed his campaign last week. “It’s urgent for Peru over time to stop thinking of itself as just an exporter of primary commodities.”

Whoever is sworn in as president July 28 will struggle to establish legitimacy.

Large-scale protests are especially likely if Fujimori wins. Meanwhile, the highly conservative outgoing Congress is ramming through constitutional changes that would curb Castillo’s powers to dissolve the body.

Tellingly, lawmakers are maintaining the current low bar for presidential impeachment. They effectively set the precedent in November, when they ousted President Martín Vizcarra on a legislative whim.

Jorge Riveros-Cayo, 52, a Lima travel agent, is one of many Peruvian voters who could not bring themselves to support either candidate. “If you think voting for Keiko is saving democracy, you’re wrong,” he says. “But so is this righteous attitude from the people who are voting for Castillo to stop corruption.”

He added: “This is like a time bomb. The longer it takes to resolve the problems facing our country, the bigger the explosion. Neither candidate has the answers.”

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