Can an intellectual on an anti-graft crusade win the presidency in a nation sliding toward authoritarianism? Guatemala is about to find out.Bernardo Arévalo had been enjoying a quiet and predictable life for nearly a decade with his family in Geneva, working on pro-democracy issues for a nonprofit. That placid existence ended after he returned to his homeland, Guatemala, and got drawn into politics.Today, whenever Mr. Arévalo appears in public, he attracts throngs to hear him assail the government’s attacks on Guatemala’s democracy.Flanked by a well-armed security detail after receiving death threats following the assassination last week of a presidential candidate in Ecuador — which sent tremors across Latin America — Mr. Arévalo wears a bullet-resistant vest and travels in an armored S.U.V.Now, in what is building into a watershed moment for Central America’s most populous country, Mr. Arévalo, a Hebrew- and French-speaking polyglot with a doctorate in sociology, is on the cusp of winning the presidency in a runoff on Sunday — an implausible scenario just months ago.“Bernardo is a glitch in the matrix,” said Edgar Ortíz Romero, a constitutional law expert and one of Guatemala’s top political risk analysts, calling Mr. Arévalo “the most progressive candidate to get this far since 1985,” when democracy was restored in the country after more than three decades of military rule.Citing moves by the nation’s electoral agency before the first round of voting in June to disqualify every serious candidate who could challenge the conservative establishment, Mr. Ortíz Romero added: “His emergence is something I never saw coming, that no one saw coming. Had that been the case, they would have disqualified him, too.”After his unexpected showing in the first round, polls suggest a landslide win for Mr. Arévalo, 64, the candidate of a small party comprised largely of urban professionals like university professors and engineers, over Sandra Torres, a former first lady considered a standard-bearer for the conservative establishment.Still, doubts persist around the results, especially because polls failed to foresee Mr. Arévalo’s earlier performance, and around whether Ms. Torres’s supporters will interfere with the voting in a country where elections are regularly marred by such attempts.Sandra Torres, a former first lady and the leading conservative candidate, has a strong base of supporters among rural voters. Daniele Volpe for The New York TimesMr. Arévalo has also come under withering attacks, including suggestions that he supports communism.Nevertheless, his surging anticorruption campaign points to a rare opening to push back against authoritarian tactics that have forced into exile dozens of judges and prosecutors focused on fighting corruption, raising fears that Guatemala is sliding into autocratic rule.His rise has been helped by deepening fatigue, in one of Latin America’s most unequal countries, with a political system in which entrenched elites enrich themselves and are seen as operating above the law.Guatemala’s current president, Alejandro Giammattei, who is prohibited by law from seeking re-election, has overseen the persecution of judges, nonprofits and journalists. His predecessor, Jimmy Morales, shut down an international body that had been prosecuting graft in Guatemala after his brother and son were arrested on corruption charges.Even Mr. Arévalo, the son of a revered Guatemalan president who is still exalted in textbooks for creating the country’s social security system and guaranteeing freedom of speech, seems a little surprised by the turn of events.In an interview this week at his aging art-deco home in a middle-class neighborhood in the capital, Guatemala City, Mr. Arévalo, goateed and wearing a blue blazer and colorful socks, recounted how he arrived at this moment.Mr. Arévalo is the son of a revered former president who established social security in Guatemala.Daniele Volpe for The New York TimesBorn in Montevideo, Uruguay, where his father took his family to live in exile after his successor as president was toppled in a 1954 C.I.A.-backed coup, Mr. Arévalo was raised in Venezuela, Mexico and Chile before his family could return to Guatemala, where he attended high school.After his father became ambassador to Israel, Mr. Arévalo started wandering again. He learned Hebrew as an undergraduate at the Hebrew University of Jerusalem, and studied political sociology in Europe, obtaining a doctorate at Utrecht University in the Netherlands. He returned to Guatemala to work as a diplomat, eventually becoming ambassador to Spain.Then he moved his family to Switzerland, where Mr. Arévalo worked for Interpeace, a nonprofit assisting post-conflict societies. Based in Geneva, he occasionally worked in African countries before deciding to return to Guatemala in 2013.“I was never interested in electoral politics,” Mr. Arévalo said. But he also didn’t want to live out his days far from Guatemala. “I wanted to get involved.”When anticorruption protests exploded in 2015, leading to the president at the time resigning and then being jailed, Mr. Arévalo joined academics, writers and intellectuals to figure out ways to seize on the momentum. While some wanted to create a new political party, Mr. Arévalo sought to establish a research institute, recalled Román Castellanos, now a member of Congress.“Those wanting the party won the debate,” said Mr. Castellanos, who represents Semilla, or Seed, the party born from those discussions.Taking advantage of name recognition, Mr. Arévalo ran for elected office in 2019 for the first time, winning a seat for Semilla in Congress.He said he was not planning to run for president until internal voting in Semilla chose him as the party’s candidate. He was driving himself in an unarmored car to campaign events and polling in the low single digits before stunning his opponents — and even many of his supporters — when he placed second in the June election.Supporters of Mr. Arévalo gathered last month in Guatemala City. Mr. Arevalo could become the country’s first progressive leader in four decades.Daniele Volpe for The New York TimesLuis von Ahn, the Guatemalan founder of the language-learning app Duolingo, said he was impressed by Mr. Arévalo’s intelligence and idealism, but when Semilla reached out for financing, he said no, believing the campaign would never gain traction.“I’m not in the practice of wasting money,” Mr. von Ahn said, describing Guatemala as a “land of sharks.” At the time, he said, he saw Mr. Arévalo as “your uncle who is an academic, who means well, but has no chance.”But after Mr. Arévalo made it to the second round, Mr. von Ahn changed his mind and contributed $100,000 to the party. He has also publicly offered to pay airfare for some of Mr. Arévalo’s most virulent critics, including officials entangled in graft scandals, to leave Guatemala, preferably for Panama, a historic destination for disgraced politicians.Guatemala’s conservative establishment has mounted an intense effort to undermine Mr. Arévalo. Shortly after the first round, Rafael Curruchiche, a prosecutor who has himself been placed by the United States on a list of corrupt Central American officials, sought to suspend Mr. Arévalo’s party.Rafael Curruchiche, a prosecutor who has been labeled as corrupt by the U.S. government, has sought to suspend Mr. Arévalo’s party, claiming irregularities in signatures gathered by the party.Daniele Volpe for The New York TimesBut that move backfired, producing calls across the ideological spectrum in Guatemala for Mr. Arévalo to be allowed to run.Still, Mr. Curruchiche this week resurrected his plan, citing allegations of irregularities in Semilla’s gathering of signatures and warning that arrests could take place after Sunday’s voting.That’s just one challenge Mr. Arévalo faces. While he leads in the polls and is forecast to perform well in most of Guatemala’s cities, Ms. Torres, the former first lady, has her own considerable base of support, especially among rural voters who embrace her calls to expand social programs, including cash transfers to the poor.Mr. Arévalo promises to create a large public jobs program by improving services like water sanitation and also proposes increasing cash transfers, but has made rooting out corruption the centerpiece of his campaign.Smear campaigns on social media, especially on TikTok and X, formerly known as Twitter, have sought to paint Mr. Arévalo as supporting abortion and gay marriage.Ms. Torres also used an anti-gay slur to refer to Mr. Arévalo’s supporters (she later said she was not homophobic). Influential evangelical Christian pastors have insinuated that Mr. Arévalo supports communism and plans to close churches.But Mr. Arévalo noted in the interview that his party stood alone in Guatemala’s Congress in seeking to condemn the authoritarian tactics of Nicaragua’s nominally leftist government.Mr. Arévalo’s ascent has been helped by the questionable disqualification of other opposition candidates by the country’s electoral body. Daniele Volpe for The New York TimesMr. Arévalo added that he has no plans to legalize abortion or gay marriage. Still, if elected, he said his government would “not permit discrimination against people because of their sexual orientation.”The campaign has changed his life in other ways. Mr. Arévalo said he had recently become aware that Guatemala’s Department of Civil Intelligence, known as DIGICI, was “monitoring me and other people in this movement on orders of superiors.” A spokesman for the ministry overseeing the intelligence agency said Mr. Arévalo was not under surveillance.As concerns for his safety have grown in the campaign’s waning days, Mr. Arévalo has increased his security detail.While his campaign has resonated among younger, urban Guatemalans, he said he has had to lean on his political lineage to reach other voters.“Here we don’t have Lincolns or FDR’s, those figures who construct a sense of national belonging,” he said. “Even so, the figure of my father remains alive. That is crucial.” More