When President-elect Donald J. Trump picked “the Great Elon Musk,” the world’s richest man, to slash government spending and waste, he mused that the effort might be “the Manhattan Project of our time.”
On Wednesday, that prediction looked spot on. Wielding the social media platform he purchased for $44 billion in 2022, Mr. Musk detonated a rhetorical nuclear bomb in the middle of government shutdown negotiations on Capitol Hill.
In more than 150 separate posts on X, Mr. Musk demanded that Republicans back away from a bipartisan spending deal that was meant to avoid a government shutdown over Christmas. He vowed political retribution against anyone voting for the sprawling bill backed by House Speaker Mike Johnson.
Mr. Musk reposted the complaints by conservative Republicans about the spending measure, celebrating each as a win. He also shared misinformation about the bill, including false claims that it contained new aid for Ukraine or $3 billion in funds for a new stadium in Washington.
By the end of the day, Mr. Trump issued a statement of his own, calling the bill “a betrayal of our country.”
It was a remarkable moment for Mr. Musk, who has never been elected to public office but now appears to be the largest megaphone for the man about to retake the Oval Office. Larger, in fact, than Mr. Trump himself, whose own vaunted social media presence is dwarfed by that of Mr. Musk.
The president-elect counts 96.2 million followers on X, while Mr. Musk has 207.9 million. (Mr. Musk is also far richer than Mr. Trump. According to the Bloomberg Billionaires Index, he is worth $442 billion, while the president-elect is worth a mere $6.61 billion.)
Mr. Trump and Mr. Musk dined at the president-elect’s Mar-a-Lago resort on Wednesday night even as Mr. Musk’s tweets were roiling Washington. Mr. Musk was not initially expected to be part of the dinner but joined as it was underway, according to two people who spoke on condition of anonymity to discuss a private dinner.
Mr. Musk and Jeff Bezos are among a string of tech billionaires who have flocked to Mr. Trump’s Florida estate. Mr. Bezos, the Amazon and Blue Origin founder who also owns The Washington Post, recently gave $1 million to the committee planning Mr. Trump’s inauguration.
On Thursday morning, Mr. Trump sought to reclaim control of the political debate for himself, issuing a threat of sorts to Mr. Johnson that he must not give in to Democrats as he tries to find a way to keep the government operating without incurring the wrath of Mr. Musk.
“If the speaker acts decisively, and tough, and gets rid of all of the traps being set by the Democrats, which will economically and, in other ways, destroy our country, he will easily remain speaker,” Trump said in an interview with Fox News Digital.
Left unclear was whether Mr. Musk is a loose cannon pursuing his own agenda or the tool that Mr. Trump envisioned to rein in an out-of-control bureaucracy when he appointed him to lead the so-called Department of Government Efficiency, or DOGE, with Vivek Ramaswamy, another billionaire.
Many House Republicans have been left deeply frustrated by Mr. Musk’s involvement in spending negotiations and legitimately concerned about his threat to find primary challengers to take on any lawmakers who vote for a spending bill he doesn’t like. Lawmakers said they were alarmed and that they have never seen a donor outwardly exact so much influence on policy after his preferred candidate won an election.
They are also stuck taking their cues from Mr. Musk’s social media feeds, where he is promoting members who are in agreement with him. Despite his occasional presence on the Hill and in his role leading DOGE, Mr. Musk does not interface directly with many members of Congress. Mr. Ramaswamy has been the one talking directly with them.
On the House floor on Thursday, lawmakers were fuming that Mr. Musk is not a member of Congress and is exerting too much influence on their proceedings. Representative Glenn Thompson, Republican of Pennsylvania and chairman of the Agriculture committee, told reporters that he “didn’t see where Musk has a voting card.”
Mr. Thompson, who was deeply involved in negotiating direct payments for farmers that are now effectively dead because of Mr. Musk, added, “I’m not sure he understands the plight of the normal working people right now.”
As their offices were flooded with calls, appropriators and lawmakers from rural areas were livid that Mr. Musk had spent the day posting on social media to effectively kill the bill. Members were glued to his nonstop feed as they walked to and from votes, and some privately expressed concerns about their own political futures if he went through with his threats.
Senator Bernie Sanders, an independent from Vermont who has long railed about the undeserved power of wealthy business executives, appeared to have reached his own conclusion, sarcastically referring to Mr. Musk, the owner of X and Tesla, as the president.
“Democrats and Republicans spent months negotiating a bipartisan agreement to fund our government,” Mr. Sanders wrote — on X, of course. “The richest man on Earth, President Elon Musk, doesn’t like it. Will Republicans kiss the ring? Billionaires must not be allowed to run our government.”
Conservative Republicans rallied behind Mr. Musk’s barrage of posts.
Representative Andy Barr, Republican of Kentucky, told Fox News that “this is exactly what the American people voted for when they voted for Donald Trump.”
After Mr. Musk threatened on X to “vote out” any member who voted for the spending bill, Representative Dan Bishop of North Carolina cheered. “In five years in Congress, I’ve been awaiting a fundamental change in the dynamic,” he wrote online. “It has arrived.”
Some Republicans even went so far as to suggest that the party should replace Mr. Johnson with Mr. Musk as speaker, noting that speaker candidates don’t have to be a sitting member of Congress to win the gavel.
“I’d be open to supporting @elonmusk for Speaker of the House,” Representative Marjorie Taylor Green of Georgia wrote on social media. She added: “The establishment needs to be shattered just like it was yesterday. This could be the way.”
That kind of lavish praise could come back to haunt Mr. Musk.
The president-elect gets famously irritable when the people in his orbit outshine him. Steve Bannon, once the chief strategist in the White House during his first term, abruptly departed after journalists focused attention on the power and influence he wielded. (One “Saturday Night Live” skit weeks into his presidency featured Mr. Bannon as the Grim Reaper standing behind the president and calling the shots in the Oval Office.)
One of Mr. Musk’s first posts about the spending bill came at 4:15 Wednesday morning in Washington.
“This bill should not pass,” the billionaire wrote on his social platform.
Between posts about his own video game antics and SpaceX’s satellite internet service, he used his X account to call the bill “criminal,” spread misinformation about its contents and issue a rallying cry to “stop the steal of your tax dollars!”
His posts followed a similar pattern of past activity on X, where he can become hyper-fixated on a single issue that bothers him. As the most popular user on X, Mr. Musk has used his feed as a bullhorn to drive conversation on the platform and beyond.
Wednesday, however, was the first time Mr. Musk has been able to use his website as a digital whip, driving lawmakers to support his desired outcome. By the afternoon, House representatives and senators — some of whom had already voiced their disapproval of the bill before Mr. Musk’s outbursts — were posting on X about their “no” votes and echoing Mr. Musk’s calls to curb spending and support the efficiency effort.
“Any Member who claims to support the @DOGE should not support this “CR of Inefficiency” that does not have offsets!!,” Representative Ralph Norman, a Republican from South Carolina, wrote on X, using shorthand for a continuing resolution to keep federal funding flowing. “Don’t get weak in the knees before we even get started!”
On Wednesday, narrative eclipsed truth. “The terrible bill is dead,” Mr. Musk posted just before 4 p.m. in Washington, closing his post with the Latin phrase “Vox Populi, Vox Dei,” which translates to “the voice of the people is the voice of God.”
He’s used the refrain before, most notably when restoring Mr. Trump’s Twitter account in November 2022, shortly after buying the company. This time, the man who spent more than a quarter of a billion dollars this election cycle to support Mr. Trump’s campaign used it to frame his own actions as the will of American citizens.
“No bills should be passed Congress until Jan. 20, when @realDonaldTrump takes office,” Mr. Musk wrote on X. “None. Zero.”
Maggie Haberman contributed reporting from New York.
