In almost every meeting that President-elect Donald J. Trump holds at Mar-a-Lago, there’s one key figure by his side who hasn’t been elected to anything, nominated for any position, and only a few months ago had no significant connection to him: Elon Musk.

The world’s wealthiest individual has quickly gained an extraordinary, though unofficial, influence within Mr. Trump’s transition team, securing a role that positions him as arguably the most powerful private citizen in America. Musk has participated in nearly every job interview with Trump’s team, developed a close bond with the Trump family, and is pushing to place his Silicon Valley associates in key positions within the incoming administration.

On Tuesday, Mr. Trump revealed that Musk would lead a new initiative, the “Department of Government Efficiency,” which aims to “dismantle government bureaucracy.” However, Musk’s influence on the transition goes far beyond this public assignment.

Musk has cultivated a near-mythical status within Trump’s inner circle. During a recent visit to Mar-a-Lago, he entered the dining room about 30 minutes after Trump and received a standing ovation from the guests, according to two sources who witnessed the event.

Over the past week, Musk, often accompanied by his 4-year-old son X, has spent the majority of his time at Mar-a-Lago, attending not only interviews but virtually every meeting and many meals with the president-elect. He briefly returned to his $35 million estate in Austin, Texas, before coming back to Mar-a-Lago for a weekend filled with meals, visits to the gift shop, and time spent on the golf course—all alongside Trump.

When a social media follower asked if he was “the first buddy,” Musk responded affirmatively.

This article draws on over a dozen interviews with Republican donors, politicians, and Musk’s close associates, many of whom requested anonymity to discuss private conversations.

Publicly, Musk has been active in supporting Trump’s transition. He has endorsed Senator Rick Scott of Florida for Senate majority leader, advised Republican senators to support Trump’s recess appointments, suggested all government employees submit a “weekly email of accomplishments,” and even proposed closing the Department of Education. Musk has also solicited recommendations for new administration roles and posted various Trump-related memes.

Privately, Musk’s involvement in the transition has been even more direct than some of his allies anticipated. In fact, some Trump aides believe Musk’s role may surpass that of Howard Lutnick and Linda E. McMahon, who are formally heading the transition effort.

Musk has participated in calls with foreign leaders, including Turkish President Recep Tayyip Erdogan and Ukrainian President Volodymyr Zelensky. He also plans to meet in person with Argentine President Javier Milei during his visit to Mar-a-Lago this week. Additionally, Musk has attended national security meetings alongside key figures such as Stephen Miller and Donald Trump Jr.

On Wednesday, Musk is expected to join Trump for a meeting with House Republicans in Washington, traveling with Trump on his plane.

Although Musk has generally refrained from nominating specific candidates for roles, he has evaluated many of the candidates already under consideration by the transition team.

Musk has expressed his approval of Trump’s decision not to appoint Mike Pompeo or Nikki Haley to senior national security roles, although he voiced concerns about Representative Elise Stefanik potentially leaving Congress for a role in the administration. Musk is also on good terms with Brendan Carr, the Federal Communications Commission commissioner, who is a front-runner to become the agency’s next chairman. Musk has privately expressed his support for Carr.

Trump spokeswoman Karoline Leavitt told The New York Times that Musk and Trump share a strong friendship and are working together to “Make America Great Again.”

On a personal level, Trump appears to have embraced Musk almost as a member of the family. A social media post by Tiffany Trump, Trump’s youngest daughter, featured a family photo with Musk standing in the center, holding his son. Trump, in the video, warmly asked, “Elon, get in the picture with your boy,” referring to Musk’s son X as “gorgeous” and “perfect.”

In a lighter moment, Trump’s grandson Kai Trump posted a picture from the golf course, captioning it, “Elon achieving uncle status.”

While Musk travels to Mar-a-Lago with a small entourage—his son, a nanny, and security—his prominence has brought a wave of influence from other Silicon Valley figures close to him.

Over the past year, Trump has cultivated relationships with right-wing figures in the tech world, particularly those supportive of his stances on cryptocurrency, AI, and Big Tech regulation. Yet, some tensions remain, as Trump’s vice president-elect, Senator JD Vance, has supported Lina Khan, the chair of the Federal Trade Commission, a figure who has clashed with Musk.

Musk has been recruiting a team of private-sector “A players” to help overhaul government operations. However, his relationships with tech executives, including those from SpaceX, raise concerns about potential conflicts of interest.

Musk has recommended Gen. Terrence J. O’Shaughnessy and Tim Hughes, SpaceX executives, for roles within the administration. He has also paved the way for other friends and associates to gain influence, including tech investor Joe Lonsdale, who is not seeking a formal role but may act as an advisor. Another associate, Ken Howery, has expressed interest in a diplomatic position, and tech investor Marc Andreessen has also been mentioned as a potential influence.

Musk has encouraged Palmer Luckey, co-founder of the military tech company Anduril, to contribute to the administration’s efforts. Luckey, in turn, has discussed potential ways to assist with the Trump team.

The friend of Musk’s who seems to have the closest ties to the administration is David Sacks, a former PayPal colleague. Sacks has developed direct communication with Trump and has pushed for Robert F. Kennedy Jr. to join the administration. Although Sacks has said that his venture capital commitments prevent him from taking a formal position, he has helped block the appointment of certain candidates, like Mike Pompeo.

Musk’s role in the Trump transition bears similarities to the one played by Peter Thiel during the 2016 election. Thiel, who had a falling-out with Trump, is still involved, passing along potential candidates for key positions.

Several figures with ties to Thiel, including former Arizona Senate candidate Blake Masters, have been involved in recommending names for the administration. Jim O’Neill, another former Thiel aide, is reportedly interested in a health-related position, and Michael Kratsios, former chief technology officer, is again involved in the tech-policy discussions.

Despite their differing relationships with Trump, both Musk and Thiel have used their influence to help shape the new administration, marking the continued intersection of Silicon Valley and American politics.