Just a few months ago, the political movement behind Brazil’s far-right former president, Jair Bolsonaro, was sputtering. Mr. Bolsonaro had been voted out of office, ruled ineligible to run in the next election and was in the cross hairs of deepening criminal investigations.

But now Mr. Bolsonaro and his followers have had a sudden surge of energy and momentum — with the help of Elon Musk and the Republican Party.

Over the past month, Mr. Musk and House Republicans have harshly criticized Alexandre de Moraes, a Brazilian Supreme Court justice who is leading investigations into Mr. Bolsonaro, over the judge’s moves to block more than 100 social media accounts in Brazil. Many of them belong to prominent right-wing pundits, podcasters and federal lawmakers who, in some cases, have questioned Mr. Bolsonaro’s election loss.

Mr. Moraes has said he is acting to protect Brazil’s democracy against attacks from the former president and his allies, who have been accused of planning a coup in 2022.

Mr. Musk has repeatedly called Mr. Moraes a “dictator” and posted dozens of times about the judge on his social network, X, accusing him of silencing conservative voices.

The House Judiciary Committee, led by Representative Jim Jordan, Republican of Ohio, published sealed court orders from Mr. Moraes last month in a report about “Brazil’s censorship campaign.” And on Tuesday, House Republicans held a hearing that cast the situation in Brazil as “a crisis of democracy, freedom and rule of law.”

While the efforts of Mr. Musk and the Republican politicians have received little attention in the United States, they are making major political waves in Brazil.

Before Mr. Musk began posting about Brazil on April 6, much of the nation’s news cycle revolved around criminal investigations into Mr. Bolsonaro. That included revelations by The New York Times that Mr. Bolsonaro made an apparent bid for political asylum at the Hungarian embassy just days after authorities confiscated his passport.

But over the past month, attention has shifted to a new question: Is the Brazilian Supreme Court stifling free speech? Brazilian media covered the debate widely, including on the cover of the nation’s top weekly magazine, Veja. One of Brazil’s leading newspapers, Folha de São Paulo, called on Mr. Moraes to stop censoring.

Amid the renewed debate, Brazil’s Congress effectively killed a long anticipated bill on combating online misinformation, and the Supreme Court said it would rule on a lawsuit that challenges Brazil’s main internet law.

That a series of online posts from Mr. Musk had such a swift impact in a foreign nation’s internal politics shows his growing influence as the owner of and perhaps the loudest voice on one of the world’s largest digital town squares.

Mr. Bolsonaro is now capitalizing on the renewed attention from powerful supporters abroad. The former president has held campaign-style rallies to attack what he says is political persecution — and to thank his foreign allies.

Mr. Musk “really stands up for freedom for us all,” Mr. Bolsonaro told thousands of people on Copacabana Beach in Rio de Janeiro last month. “He’s a man who’s had the courage to show — already with some evidence, and more will surely come — where our democracy is heading and how much freedom we’ve lost.”

Mr. Bolsonaro then called for a round of applause for Mr. Musk, earning one of the biggest roars of the day. Some Bolsonaro supporters wore Elon Musk masks, while others carried signs praising the billionaire.

“With a few tweets, Elon Musk was capable of changing the political environment in Brazil,” said Ronaldo Lemos, a Brazilian lawyer who studies the nation’s internet laws. The Brazilian right was struggling, Mr. Lemos added. “He brought the energy back.”

To Brazil’s left, however, Mr. Musk and Republicans are twisting facts to attack Brazil’s institutions.

President Luiz Inácio Lula da Silva, a leftist, took on Mr. Musk in a speech last month, calling him “an American businessman who has never produced a foot of grass in this country, daring to speak ill of the Brazilian court, Brazilian ministers and the Brazilian people.”

In recent years, Brazil’s Supreme Court has taken an aggressive stance against certain online content, including election misinformation and attacks on democratic institutions. Brazilian courts have ordered X to take down at least 140 accounts since 2022, according to documents published by the House Judiciary committee.

Mr. Moraes, who declined to comment for this article, has called such measures necessary in the face of threats to Brazil’s democracy posed by Mr. Bolsonaro and some of his supporters, who ransacked Brazil’s halls of power last year. “Freedom of speech is not freedom of aggression,” Mr. Moraes said last month. “Freedom of speech is not freedom to defend tyranny.”

But his moves have also generated intense debate over whether they are posing their own threat to Brazil’s democracy.

Mr. Moraes has ordered X to suspend the accounts of some of Brazil’s most popular right-wing pundits, as well as those of at least 10 federal lawmakers, though most of the lawmakers have since returned to the platform.

In some cases, the accounts cast doubt on election results or encouraged protesters calling for a military coup. But Mr. Moraes typically seals such orders, so people who have their accounts suspended usually receive little information why.

Social networks do frequently block content that violate their policies. After the riot at the U.S. Capitol on Jan. 6, 2021, for instance, Twitter removed 150,000 accounts linked to the conspiracy movement known as QAnon, which had inspired many rioters.

But Mr. Moraes has often ordered the removal of content that social media companies would otherwise leave up under their rules.

In 2022, Mr. Moraes authorized Brazilian federal agents to raid the homes of eight major businessmen and ordered social networks to suspend some of their accounts. He was acting in response to leaked screenshots that showed two of the businessmen saying in a private WhatsApp group that they would prefer a military coup to Mr. Lula’s victory in that year’s presidential race.

Mr. Moraes shelved the investigation against most of the men last year, but has maintained the suspension of the accounts belonging to two of the businessmen, including Luciano Hang, a department store magnate. Mr. Hang, one of Mr. Bolsonaro’s most prominent backers, has been unable to use his social media accounts in Brazil, which collectively had more than six million followers, for nearly two years.

Such stories have attracted the attention of some Republicans in Congress. In the hearing on Tuesday, Representative Chris Smith, a New Jersey Republican, said that “Brazilians have been subject to grave human rights violations committed by Brazilian officials on a vast scale.”

But Representative Susan Wild, a Pennsylvania Democrat, said that the Brazilian courts had the mandate to prevent the sort of military dictatorship that ruled the country from 1964 to 1985. Any debate about the role of the courts in Brazil “should be decided by the Brazilian people,” she said. “The United States Congress is not the forum.”

Few U.S. lawmakers attended the hearing, but some of the biggest names on Brazil’s right did, including Mr. Bolsonaro’s son, Eduardo. The proceedings were frequently interrupted by cheering or booing from the right-wing Brazilians in attendance.

One witness, Fabio de Sa e Silva, a Brazilian lawyer and professor at the University of Oklahoma, said that he believed Brazilian law supported Mr. Moraes’s right to block accounts. He argued that any crisis in Brazil’s democracy was not because of judges but rather because of “mobs unwilling to play by the rules.”

But some analysts argue that Mr. Moraes appears to be violating Brazilians’ rights. Mr. Lemos, the Brazilian internet law expert, said that he no longer saw such an extreme threat to Brazil’s democracy that would justify Mr. Moraes’s aggressive approach.

“We’re no longer living through an emergency,” he said.