Tens of thousands of people demonstrated in cities across Brazil, many of them demanding that the military stop the transfer of power to President-elect Luiz Inácio Lula da Silva.BRASÍLIA — They arrived by the tens of thousands on Wednesday, angry and draped in Brazilian flags, massing outside military bases across the country. They were there, they said, to save Brazil’s democracy from a rigged election, and there was only one way to do so: The armed forces needed to take control of the government.It was an alarming demand in a country that suffered under a two-decade military dictatorship until 1985 — and yet another bizarre twist in the aftermath of Brazil’s polarizing elections.A day earlier, the far-right president, Jair Bolsonaro, reluctantly agreed to a transfer of power after 45 hours of silence following his loss to a leftist former leader, Luiz Inácio Lula da Silva. But after Mr. Bolsonaro’s years of unfounded attacks on Brazil’s election systems, his supporters appeared far from accepting defeat.Andrea Vaz, a supporter of President Jair Bolsonaro, holds a sign claiming fraud in the presidential election outside the army headquarters on Wednesday.Dado Galdieri for The New York Times“I don’t understand it that well, but they have to intervene and hold new elections,” said Andrea Vaz, 51, a computer-hardware seller holding a sign that said, “Fraud in the voting machines!” at a large protest outside the Brazilian Army’s national headquarters in Brasília. “We saw various videos. People giving out money, buying votes,” she added. “There’s proof.”But some protesters had clearer, more drastic demands, which were circulating on WhatsApp and Telegram groups: The military should take control of the streets, the Congress and the Supreme Court should be disbanded, and the president should remain in power, at least until new elections could be held.The widespread protests and calls for the armed forces were an escalation of the Brazilian far-right’s refusal to accept the election of Mr. da Silva, a former president whom many on the right view as a criminal because of his past corruption scandal.Mr. Bolsonaro, in a two-minute speech on Tuesday in which he did not acknowledge his loss, said he supported peaceful protests inspired by “feelings of injustice in the electoral process.”Many of his followers saw that as a stamp of approval. “What he said yesterday, that gave me more energy to come,” said Larissa Oliveira da Silva, 22, who was sitting on a beach chair in the protest in São Paulo, propping up her broken foot. “After his comments, I saw that he is on our side.”But other protesters said that Mr. Bolsonaro had effectively given up with his agreement to transfer power to Mr. da Silva on Tuesday, so they were turning to the armed forces instead.In a statement, Brazil’s Ministry of Defense said that “the demonstrations, provided they are orderly and peaceful, are the exercise of freedom of expression, of thought, and of assembly, in accordance with constitutional principles and current laws.”The military has not considered intervening in the transfer of power and, if the protests expand, it may urge the president to ask his supporters to go home, according to a senior military official who spoke on the condition of anonymity to describe private talks. The military, which helped oversee the election, found no signs of fraud, the official said.The Ministry of Defense said that it would soon deliver its report on the vote’s integrity to election officials.In interviews with more than 60 protesters across Brazil since Sunday, almost none believed the election was clean. Those beliefs were rooted in the same circumstantial evidence, unattributed reports and inaccuracies that Mr. Bolsonaro has promoted for years to claim that Brazil’s elections are rife with fraud. They had seen videos of the voting machines malfunctioning, read that patterns in the vote returns were suspicious and, they said, they simply did not trust election officials.Most of all, however, they said that Mr. Bolsonaro had drawn much bigger crowds than Mr. da Silva — and almost everyone they knew voted for the president — so how could it be that he lost?The movement was loosely organized. There appeared to be no formal protest leaders, and prominent public figures, including conservative politicians, did not echo similar calls for intervention. Yet it quickly grew into the largest demonstration since Mr. Bolsonaro lost the vote on Sunday..css-1v2n82w{max-width:600px;width:calc(100% – 40px);margin-top:20px;margin-bottom:25px;height:auto;margin-left:auto;margin-right:auto;font-family:nyt-franklin;color:var(–color-content-secondary,#363636);}@media only screen and (max-width:480px){.css-1v2n82w{margin-left:20px;margin-right:20px;}}@media only screen and (min-width:1024px){.css-1v2n82w{width:600px;}}.css-161d8zr{width:40px;margin-bottom:18px;text-align:left;margin-left:0;color:var(–color-content-primary,#121212);border:1px solid var(–color-content-primary,#121212);}@media only screen and (max-width:480px){.css-161d8zr{width:30px;margin-bottom:15px;}}.css-tjtq43{line-height:25px;}@media only screen and (max-width:480px){.css-tjtq43{line-height:24px;}}.css-x1k33h{font-family:nyt-cheltenham;font-size:19px;font-weight:700;line-height:25px;}.css-1hvpcve{font-size:17px;font-weight:300;line-height:25px;}.css-1hvpcve em{font-style:italic;}.css-1hvpcve strong{font-weight:bold;}.css-1hvpcve a{font-weight:500;color:var(–color-content-secondary,#363636);}.css-1c013uz{margin-top:18px;margin-bottom:22px;}@media only screen and (max-width:480px){.css-1c013uz{font-size:14px;margin-top:15px;margin-bottom:20px;}}.css-1c013uz a{color:var(–color-signal-editorial,#326891);-webkit-text-decoration:underline;text-decoration:underline;font-weight:500;font-size:16px;}@media only screen and (max-width:480px){.css-1c013uz a{font-size:13px;}}.css-1c013uz a:hover{-webkit-text-decoration:none;text-decoration:none;}What we consider before using anonymous sources. Do the sources know the information? What’s their motivation for telling us? Have they proved reliable in the past? Can we corroborate the information? Even with these questions satisfied, The Times uses anonymous sources as a last resort. The reporter and at least one editor know the identity of the source.Learn more about our process.With a collective turnout of well over 100,000 people, protesters gathered in at least 75 cities, including in all of Brazil’s 27 state capitals, often around military bases.Police clashed with pro-Bolsonaro protesters blocking the Castelo Branco highway in São Paulo on Wednesday.Victor Moriyama for The New York TimesElsewhere across the country, protesters continued to set up highway blockades, creating miles-long backups and disrupting transportation and freight. Those blockades began immediately after the election results on Sunday as part of what protesters said was an effort to “paralyze” Brazil and force the military to intervene. As of Wednesday afternoon, 146 blockades were still active, according to the federal highway police.Around São Paulo, the blockades caused multiple backups totaling more than 60 miles of traffic jams on Wednesday, according to the local traffic agency, and led to the cancellation of 1,400 buses. The disruptions also caused fuel shortages in at least four states.Mr. Bolsonaro released a video late Tuesday, pleading with his supporters to stop blocking the roads, saying it was disrupting lives and hurting the economy. “I am as upset and sad as you are, but we have to put our heads in the right place,” he said. “Other demonstrations that are taking place across Brazil in public squares are part of the democratic game.”“Let’s do what has to be done,” he added. “I’m with you.” He did not directly address the calls for military intervention.The protests were largely nonviolent. The most notable incident was an attack against protesters in Mirassol, a midsize city north of São Paulo, when a car drove into the crowd, injuring 11 people, according to local police. One man was arrested on attempted murder charges, police said.Beyond their insistence that the vote was stolen, the protesters were also driven by their disdain for Mr. da Silva, who has been the most dominant political figure in the 34 years of Brazil’s modern democracy. Universally known as Lula, he has been a top candidate in six of the nine presidential elections over that stretch, winning three.But after his last administration, he also served 17 months in prison on corruption charges, which were later thrown out when the Supreme Court ruled the judge in his cases was biased.He was never cleared of any wrongdoing, however, fueling a belief that he is not to be trusted and making him perhaps a more polarizing force for many Brazilians than Mr. Bolsonaro.Danielle Mota holds a banner calling for intervention in the election outside army headquarters on Wednesday.Dado Galdieri for The New York Times“We don’t want a thug president who robbed, who was arrested, who had various people in his government who looted Brazil,” said Danielle Mota, 43, a hairdresser holding a sign that said “Federal Intervention.”“We do want a military intervention.” she added. “Just like in 1964.”That was the year that the armed forces, with U.S. support, overthrew the government, instituting a military dictatorship for 21 years that killed or tortured thousands of political opponents. Most protesters interviewed on Wednesday at demonstrations in three of the country’s largest cities, Brasília, São Paulo and Rio de Janeiro, said they wanted Brazil to remain a democracy. But others, faced with Mr. da Silva as president, said it was time for a military government.“Permanently,” said Kenya Oliveira, 38, holding her 4-year-old son.Camila Rocha, a Brazilian political scientist who wrote a book on the radicalization of Brazil’s right, said the calls for the military were the product of years of absorbing Mr. Bolsonaro’s claims that the elections were rigged, combined with fears of a da Silva administration.Mr. da Silva’s leftist Workers’ Party was at the center of a sprawling government kickback scheme that was revealed after he left office in 2010, leading to the imprisonment of many of the party’s top officials. Mr. Bolsonaro and his allies have long called the party corrupt, but they have also falsely framed it as communist.Many on the right view Mr. da Silva “not as an adversary, but as an enemy that needs to be contained,” Ms. Rocha said. “In this sense, there is a strong parallel with the 1964 coup, which was justified precisely to halt the advance of what was thought to be the rise of communism in Brazil.”Many of the protesters said their demands for intervention were supported by Article 142 of the Brazilian Constitution, which says that the military has the role of “guaranteeing constitutional powers” under the “supreme authority of the president.”According to constitutional lawyers and past court rulings, the article does not allow the military to take control of the government.Marco Aurélio Mello, a retired Supreme Court Justice and an outspoken supporter of Mr. Bolsonaro, said the protesters’ interpretation is merely “nostalgia for the authoritarian regime.”He added that instead the protesters had “the losers’ right to whine.”Laís Martins contributed reporting from São Paulo, Flávia Milhorance, Ana Ionova and Leonardo Coelho from Rio de Janeiro, and André Spigariol and Gustavo Freitas from Brasília. 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