“My America PAC massively improved the Republican ground game in the swing states,” Mr. Musk told the conservative commentator Tucker Carlson in an interview at Mar-a-Lago, Mr. Trump’s residence and private club in Florida. He posted a meme of himself in the Oval Office for his 203 million followers on X, his social media platform.

His victory lap was the culmination of an effort that began only six months ago and depended on a risky gamble: Mr. Musk’s new super PAC effectively led Mr. Trump’s get-out-the-vote operation in battleground states — and Mr. Trump entrusted a crucial campaign function to a political neophyte.

It is difficult to disentangle Mr. Musk’s ground work from other influences that propelled Mr. Trump to the White House. But there is little doubt that the election was a win not only for Mr. Musk but also big-money politics: An ultrawealthy donor took advantage of America’s evolving campaign-finance system to put his thumb on the scale like never before.

Mr. Musk almost single-handedly funded an effort that cost more than $175 million. His canvassers knocked on close to 11 million doors in presidential battleground states since August, including about 1.8 million in Michigan and 2.3 million in Pennsylvania, according to people with knowledge of the matter. Another $30 million was spent on a large direct-mail program, and about $22 million on digital advertising, including on Trump-friendly mediums like Barstool Sports.

When Mr. Musk first met with political advisers in the spring, he focused on turning out 800,000 to a million “low-propensity” voters in seven battleground states — people, especially in rural areas, who might be inclined to vote for Mr. Trump but who had spotty voting records. It is yet unclear whether Mr. Musk succeeded on that metric, although Mr. Trump claimed a dominating margin in rural areas, a focus of Mr. Musk’s.

The super PAC’s apparent success could inspire similar efforts, helping to transform modern campaigns. New guidance from the Federal Election Commission, issued in March, now allows presidential campaigns to closely coordinate field operations with super PACs.

“There is no reason to expend the precious hard money of federal campaigns on ground game activities if there are outside organizations with a proven track record and a verifiable infrastructure,” said the conservative activist Ralph Reed, whose own super PAC, the Faith and Freedom Coalition, said it knocked on close to 10 million doors on Mr. Trump’s behalf.

Mr. Musk leaned heavily on time-tested voter turnout tactics. On Tuesday, for example, he highlighted that he had offered a “fleet of vehicles” to Trump voters, including to the Amish community in Pennsylvania, whose members do not drive cars.

He prioritized early and absentee voting even though Mr. Trump had spent years deriding it. After Mr. Musk’s senior leadership team went into the field themselves in late August, they adjusted canvassers’ scripts to focus on not only identifying Trump supporters but also encouraging absentee voting and providing a QR code to request a mail-in ballot.

But Mr. Musk, as he often does, also pushed boundaries. He offered financial incentives to potential voters, including $1 million gifts for people who signed a petition supporting free speech and the right to bear arms. The stunt, which prevailed over a lawsuit from the district attorney of Philadelphia, attracted mounds of free publicity. The Justice Department cast doubt on the legality of the effort but has not challenged it in court.

And Mr. Musk became one of Mr. Trump’s top cheerleaders and surrogates. On X, his account, the most-followed on the platform, became a pro-Trump megaphone, including sharing misinformation about voter fraud and conspiracy theories.

Trump campaign officials largely appreciated Mr. Musk’s help, even if there was uncertainty among his senior brass about the wisdom of depending on him.

Mr. Musk, who received daily reports on early vote totals, assembled a team of both traditional Republican operatives and personal friends, some of whom temporarily relocated to Pennsylvania conference rooms and hotels. One of Mr. Musk’s most trusted lieutenants, Steve Davis, was particularly involved, offering ultra-specific feedback on canvassers’ scripts, for instance, according to two people with knowledge of the matter.

After several dramatic, costly summer staffing hiccups, Mr. Musk scaled his program on a very short runway — assigning a state director to each battleground, who was tasked with hiring door-knocking firms that could find those infrequent Trump voters. Flush with his resources, Mr. Musk’s super PAC also pushed a phone call program in the final days to push even “mid-propensity” voters to go support Mr. Trump.

The other key moment came in early October, when Mr. Musk, who had kept the super PAC at an arm’s length publicly, signed off on an effort to merge his personal brand with that of America PAC. Mr. Musk also saw how close Pennsylvania was shaping up to be and decided to push resources to the state, including his own time.

Mr. Musk’s operation was hardly perfect.

Accusations of fraud among low-paid canvassers dogged the operation and raised internal concerns among executives. In the final days, the main software used by canvassers had significant glitches, leading to what organizers said were problems in Wisconsin and Nevada.

Mr. Musk’s super PAC had also hoped for a dramatic surge of door-knocking in the final days in key states — as many as 5,500 canvassers in the field. In Michigan, the super PAC offered $200 daily bonuses to canvassers to recruit additional labor for the final hours. But several people involved in the operation said they saw no such surge. In Wisconsin, for instance, people could not be hired on such short notice.

He all but claimed sole success for a registration surge and strong early-voting numbers among Republicans in Pennsylvania, but other entities pushed the same message there. One of them, Americans for Prosperity, the grass-roots group funded by Charles Koch, said it knocked on a million doors in Pennsylvania.

Mr. Musk, who had held town halls and appeared at rallies for Mr. Trump, tapered off at the end. He canceled one town hall on Monday that was marred by technical difficulties, and skipped another on Tuesday without explanation, only to launch a different conference call on X Spaces later that afternoon.

Mike DuHaime, a former official at the Republican National Committee, expressed a skittishness about the lessons that campaigns might draw from Mr. Trump’s victory with the billionaire’s help.

“It’s really empowered these kind of big-money donors to be able to have a massive influence on politics,” he said. “I think the more spending that’s controlled by the campaigns and by the political parties, the better, because they’re the ones who are ultimately accountable to the voters.”

Fueled by mutual admiration, Mr. Musk and Mr. Trump may have formed a lasting political alliance. “A star is born — Elon!” Mr. Trump said in his victory speech, before retelling several stories about Mr. Musk’s business accomplishments.

As his plane landed Tuesday night near Mar-a-Lago, Mr. Musk said on an X livestream that he had no plans to curtail his political ambitions, and that his super PAC would “weigh in heavily” on judicial races and the 2026 midterms. “America PAC is going to keep going after this election,” he said.

Mattathias Schwartz and Kenneth P. Vogel contributed reporting.