Minutes after it became clear that Javier Milei had been elected president of South America’s second-largest nation in November, Elon Musk posted on X: “Prosperity is ahead for Argentina.”

Since then, Mr. Musk has continued to use X, the social network he owns, to boost Mr. Milei. The billionaire has shared videos of the Argentine president attacking “social justice” with his 182 million followers. One doctored image, which implied that watching a speech by Mr. Milei was better than having sex, is among Mr. Musk’s most viewed posts ever.

Mr. Musk has helped turn the pugnacious libertarian into one of the new faces of the modern right. But offline, he has used the relationship to press for benefits to his other businesses, the electric carmaker Tesla and the rocket company SpaceX.

“Elon Musk called me,” Mr. Milei said in a television interview weeks after taking office. “He is extremely interested in the lithium.”

Mr. Musk has declared lithium — the silvery-white element that is the main component in Tesla’s car batteries — “the new oil.” Tesla has long bought lithium from Argentina, which has the world’s second-largest reserves. Now Mr. Milei is pushing for major benefits for international lithium miners, which would likely give Tesla a more stable — and potentially cheaper — flow of one of its most critical resources.

Mr. Milei is part of a pattern by Mr. Musk of fostering relationships with a constellation of right-wing heads of state, with clear beneficiaries: his companies and himself.

Mr. Musk, 52, has repeatedly used one piece of his business empire — X, formerly known as Twitter — to vocally support politicians like Mr. Milei, Jair Bolsonaro of Brazil and Narendra Modi of India. On the platform, Mr. Musk has backed their views on gender, feted their opposition to socialism and aggressively confronted their enemies. Mr. Musk even personally intervened in X’s content policies in ways that appeared to aid Mr. Bolsonaro, two former X employees said.

Mr. Musk, in turn, has pushed for and won corporate advantages for his most lucrative businesses, Tesla and SpaceX, according to an examination by The New York Times. In India, he secured lower import tariffs for Tesla’s vehicles. In Brazil, he opened a major new market for Starlink, SpaceX’s satellite internet service. In Argentina, he solidified access to the mineral most crucial to Tesla’s batteries.

Mr. Musk’s endorsement has given many nationalist and right-wing heads of state more international cachet, which they have eagerly promoted as a validation of their policies and popularity. Last month, as India began holding an election, Mr. Modi prepared to host Mr. Musk in New Delhi, calling the billionaire’s visit a testament to his leadership.

“People are coming, and they are trusting me,” the Indian prime minister said in a televised interview before Mr. Musk postponed his trip.

Mr. Musk, Tesla, SpaceX and X did not respond to requests for comment.

No other American megabillionaire businessperson has so publicly fostered ideological relationships with world leaders to advance personal politics and businesses. Bill Gates, Microsoft’s co-founder turned philanthropist, engaged in political diplomacy largely after stepping back from corporate life. Other chief executives typically stay quiet about meetings with politicians.

Mr. Musk’s politics have long been guided by his businesses, said five former Tesla and SpaceX executives who worked closely with him and were not authorized to speak publicly. In the 2010s, he built an alliance with President Barack Obama as Tesla and SpaceX welcomed federal assistance and contracts. He remains close to some mainstream leaders, notably President Emmanuel Macron of France.

But as populism and nationalism spread, Mr. Musk courted Xi Jinping in China and supported Benjamin Netanyahu in Israel, Turkey’s Recep Tayyip Erdogan and Italy’s Giorgia Meloni. He began criticizing the “woke mind virus” and what he has declared the failings of the left, which he says have led to issues such as illegal immigration and declining birthrates.

“I guess if you consider fighting the woke mind virus, which I consider to be a civilizational threat, to be political, then yes,” Mr. Musk said in a podcast in November when asked if he was becoming more political. “Woke mind virus is communism rebranded.”

INDIA

A Long Game

In September 2015, Mr. Musk welcomed Mr. Modi to Tesla’s factory in Fremont, Calif. Mr. Modi, a Hindu nationalist politician, had been elected India’s prime minister a year earlier when his Bharatiya Janata Party swept to power, and was visiting the United States to meet business leaders.

Standing under Indian and U.S. flags at the factory, Mr. Musk and Mr. Modi posed for photographs near a gleaming red Model S car. They discussed how “solar panels and battery packs” could power rural regions in India without electrical lines, Mr. Musk said at the time.

“I understood his vision,” Mr. Modi later said.

It was one of the first instances of Mr. Musk’s publicly meeting a nationalist leader. And it was the beginning of a long game between him and Mr. Modi, a relationship that took years to develop — and that started paying off for Mr. Musk after he bought X.

India is a potentially massive market for Tesla, which needs to expand to new regions to grow. But the country has virtually barred electric vehicles built by foreign manufacturers. In recent years, the tariff India imposes on imported electric vehicles has risen as high as 100 percent.

Mr. Musk initially used traditional personal diplomacy, meeting with Mr. Modi and ordering his staff at Tesla to get close to officials. In 2017, Tesla sent a letter to India’s government to kick-start talks on operating in the country. Another overture to Mr. Modi’s government in 2019 was rebuffed, three people with knowledge of the company said.

After Mr. Musk bought Twitter in 2022, he had a new lever. The platform, renamed X, is widely used in India — including by Mr. Modi, who has nearly 98 million followers — and is a major forum of political discussion.

Before Mr. Musk owned the platform, Twitter tangled with Mr. Modi’s government. The company, which complies with requests to block certain content in India, had sued the government and challenged its power to censor online material.

Under Mr. Musk, X blocked posts last year that linked to a BBC documentary examining Mr. Modi’s role in the 2002 Hindu-Muslim riots in Gujarat, where he was the chief minister at the time. Twitter’s lawsuit against the Indian government was dismissed in July.

In a discussion last year with Twitter employees, Mr. Musk intimated that he was personally close with Mr. Modi. He said he could easily call the prime minister to take care of a content issue, two former employees said. It’s unclear if any conversation took place.

Mr. Musk met Mr. Modi in person again last June when the prime minister visited New York. He called himself a “fan of Modi” and said Mr. Modi was “pushing us to make significant investment in India, which is something that we intend to do.”

By then, Tesla employees were again talking with Mr. Modi’s advisers about a reduction in tariffs and investing in India, two people familiar with the conversations said. Rohan Patel, who was Tesla’s vice president of public policy and business development, traveled to India several times, and Piyush Goyal, India’s commerce minister, visited the Fremont factory in November.

In January, Mr. Musk posted on X that India should receive a permanent seat on the United Nations Security Council, which would boost India’s international standing. “India not having a permanent seat on the Security Council, despite being the most populous country on Earth, is absurd,” he wrote.

The timing suggests that Mr. Modi noticed. Two months later, India announced it was reducing some import duties for electric carmakers that committed at least $500 million to produce vehicles in the country. The policy dropped tariffs to 15 percent of a car’s price from 100 percent, specifically for electric vehicles that retail for more than $35,000.

The description fit Tesla to a T. Its Model 3 cars ship at $38,990. BYD, the fast-growing Chinese electric vehicle maker, is barred from investing in India on national security grounds.

Last month, Tesla scouted potential factory sites in three Indian states, three people familiar with the process said. Mr. Musk had also said he would visit Mr. Modi in New Delhi during the country’s multiweek general election, before delaying the trip, citing obligations with Tesla.

Mr. Musk promised not to stay away for long. “I do very much look forward to visiting later this year,” he wrote on X.

BRAZIL

‘True Legend of Freedom’

By 2021, Mr. Musk was employing a similar courtship to bring his Starlink satellite internet service to Brazil, which was then led by Mr. Bolsonaro, the right-wing populist president elected three years earlier. At the time, Starlink was in its infancy, with fewer than 150,000 users across 25 countries.

In October 2021, Fábio Faria, Brazil’s communications minister and an organizer of Mr. Bolsonaro’s re-election campaign, sent a letter to Mr. Musk, saying that “Starlink and Brazil can become great partners,” according to correspondence obtained through the country’s open records laws.

Weeks later, Mr. Faria visited Mr. Musk in Texas. After returning to Brazil, Mr. Faria pushed regulators to approve Starlink, at one point urging Brazil’s space agency to stay out of any debate about SpaceX’s satellites over the country, he later testified to Brazil’s Congress.

Brazil’s regulators approved Starlink for operation in December 2021, seven months after the service first applied. It was the fastest of five approvals that regulators granted to satellite internet providers.

Mr. Musk later lent a hand to Mr. Bolsonaro, who faced an uphill battle in his 2022 re-election campaign.

On May 20 that year, Mr. Musk made a surprise trip to Brazil for a major announcement alongside the president. Starlink was coming to the country, and it would provide internet connectivity to 19,000 rural schools, as well as environmental monitoring of the Amazon, they said at an event in a resort near São Paulo. Mr. Bolsonaro gave Mr. Musk a medal and called him a “true legend of freedom” for his bid that year to buy Twitter.

There was just one catch: The plan to connect schools never materialized, said Carlos Baigorri, Brazil’s chief telecommunications regulator, who helped approve Starlink’s entry into the country. “I don’t really think that it even existed,” he said of the plan.

Brazilian officials said they had no record of Starlink’s connecting Brazilian schools for free or conducting environmental monitoring.

Mr. Musk and Mr. Bolsonaro benefited anyway. Mr. Musk had entrenched SpaceX in a critical market, where Starlink now has 150,000 active accounts, according to Brazil’s telecommunications regulator. Mr. Bolsonaro’s campaign got to promote the president’s business acumen and cast him as a defender of the Amazon before an election.

Mr. Musk’s favor did not prevent Mr. Bolsonaro from losing the presidency to Luiz Inácio Lula da Silva, Brazil’s leftist former president, in October 2022. But within weeks, Mr. Musk, who had just completed his deal for Twitter, tried helping Mr. Bolsonaro again.

Mr. Bolsonaro’s supporters had started pushing accusations on Twitter that Brazilian judges had tilted the election by ordering social networks to remove right-wing posts and accounts. As they camped outside military bases demanding the election be overturned, Mr. Musk fed their suspicions by suggesting that Twitter’s former bosses had contributed to Mr. Bolsonaro’s defeat.

“It’s possible that Twitter personnel gave preference to left wing candidates,” he posted in December 2022, without citing any evidence. He later wrote that the company “may have people on the Brazil team that are strongly politically biased.”

Mr. Musk got involved in deciding which posts about Brazil’s election results should stay up or be taken down, two former Twitter employees said. Even after Mr. Musk was briefed about the risk of violence in Brazil that winter, he ordered employees to stop enforcing Twitter’s election rules in the country, including a policy forbidding users to spread misleading claims about election results, they said. He told them to remove only posts that directly incited violence or were subject to a court order.

In January 2023, thousands of Mr. Bolsonaro’s supporters stormed Brazil’s Congress, Supreme Court and presidential offices, under the false belief that the election had been stolen.

Mr. Musk has since used X to attack one of Mr. Bolsonaro’s main political opponents, Alexandre de Moraes, a Brazilian Supreme Court justice who has overseen investigations into the former president and his supporters. X has blocked more than 100 accounts on orders from Justice Moraes, who has said many of them threatened Brazil’s democracy.

“This judge has brazenly and repeatedly betrayed the constitution and people of Brazil,” Mr. Musk posted on X in April. “He should resign or be impeached.”

At a rally called by Mr. Bolsonaro in Rio de Janeiro last month, his supporters held signs thanking Mr. Musk.

When Mr. Bolsonaro addressed the crowd, he hailed the billionaire as “the man who really preserves true freedom for us all.”

ARGENTINA

A Meeting of the Minds

In 2022, one of Tesla’s lithium suppliers announced a $1.1 billion investment to expand in Argentina. Since then, Mr. Musk has taken a keen interest in Argentine politics — and particularly Mr. Milei — leading to one of the most pronounced bromances among Mr. Musk’s political relationships.

Mr. Milei “would be quite a change,” Mr. Musk wrote on X in September in response to a post from the former Fox News host Tucker Carlson, who had called the then-candidate “Argentina’s next president.”

Mr. Milei, a libertarian economist and TV pundit, campaigned on getting the government out of the economy and tying Argentina more closely to the United States. Like Mr. Musk, he frequently insults critics, has an intense social media habit and is deeply worried about the threat from “woke” culture.

Days before Mr. Milei’s inauguration in December, they spoke directly for the first time, and Mr. Musk asked about Argentina’s lithium. In the months since, Mr. Milei has been pushing legislation that would make extracting Argentina’s lithium far more attractive to foreign investors.

His sweeping bill, which would grant him broad emergency powers over Argentina’s economy and energy for the next year, includes a major benefit for Tesla: significant incentives for foreign investors in large projects, particularly in mining.

Such companies would receive substantial tax cuts, customs exemptions and foreign-exchange benefits, as well as tax and regulatory certainty for the next 30 years. Tesla’s lithium supplier is likely to qualify. If so, Mr. Milei’s plan would give Tesla unusual stability and predictability in its access to lithium in Argentina until at least 2054.

The proposal passed Argentina’s lower chamber of Congress on April 30.

Mr. Musk has already seen other dividends from Mr. Milei. In one of his first acts as president, Mr. Milei passed an executive order with 366 provisions. When summarizing the highlights of the order in a televised address, Mr. Milei mentioned just one corporate brand by name: Starlink.

SpaceX had pushed for Starlink’s approval in Argentina since 2022, but faced a bureaucratic jam. Mr. Milei quickly cut regulations on satellite internet, and Starlink began operating in the country in March.

Mr. Milei, in turn, has benefited: Mr. Musk has become his most influential online promoter. In January, Mr. Musk shared videos of Mr. Milei’s speech at the World Economic Forum, in which the leader claimed communism and social justice were the main threats to the West.

The posts set off a frenzy of praise for the Argentine across right-wing corners of the internet, including from Donald J. Trump, the presumptive Republican presidential nominee, who met with Mr. Milei in February at the Conservative Political Action Conference outside Washington. Mr. Milei hugged Mr. Trump and told him he was rooting for him.

Last month, Mr. Milei traveled to Austin, Texas, to visit Mr. Musk at Tesla’s factory there. The two men agreed to “open markets and defend the ideas of freedom,” according to a statement from Mr. Milei’s office. The statement did not mention lithium.

Later, Gerardo Werthein, Argentina’s ambassador to the United States, told the Argentine newspaper La Nación that the pair had indeed discussed Argentina’s mineral reserves.

Mr. Musk “had a very good view of everything we have,” Mr. Werthein said, “especially lithium.”

On Monday, Mr. Musk and Mr. Milei met again, this time at a conference in Los Angeles. Mr. Milei called the entrepreneur “my friend” in a speech in which he praised Mr. Musk’s effort to reach Mars. A few hours later, Mr. Musk posted a photo of the two men with their thumbs up.

“I recommend investing in Argentina,” he wrote.

Reporting was contributed by Jason Horowitz from Rome, Kate Conger from San Francisco, Sameer Yasir from New Delhi, Paulo Motoryn from Brasília, Lucía Cholakian Herrera from Buenos Aires and Ishaan Jhaveri from New York.