After his exit last week, he's back on the sidelines. And it's the Trump administration, and the massive budget bill the president is currently promoting, that has drawn the ire of this new, seemingly unchecked Musk.

On Tuesday, in a series of social media posts, he attacked Trump's signature tax and spending bill, which is now being considered by the Senate after House Republicans passed it last month.

After saying he couldn't "take it anymore," Musk called the bill a "disgusting abomination."

"Shame on those who voted for it," he said. "They know they did wrong."

On Wednesday afternoon, he went a step further, asking voters to contact their representatives in Congress to voice their opposition. “Bankrupting America is not okay!” he wrote on X. “KILL the PROJECT.”

Musk’s tirade against the Trump-backed bill, which includes huge tax cuts and more defense investment, comes after he spent months calling for cuts to government spending.

In his posts, he said the legislation would increase the U.S. budget deficit and burden Americans with debt.

He also issued a warning against Republicans who supported, or plan to support, the bill: “We will fire every politician who betrayed the American people” in next year’s midterm elections.

And that line might be the most troubling for Republicans.

The Republicans’ dilemma

Every Republican in the House of Representatives,All but three members supported the bill, which passed by a single vote over unified opposition from Democrats.

If Musk turns on most Republicans, after spending hundreds of millions supporting his campaigns last year, it could cause headaches for members of Congress worried about facing primary challenges.

It could also deal a devastating blow to Republican hopes of maintaining control of Congress during the second half of Trump's second term.

While Musk had offered more measured criticism in an interview last week, this week marks a dramatic shift from the friendly Oval Office meeting he had with Trump on Thursday, in which he smiled as Trump outlined the significance of what he said will be his defining legislative achievement.

The president has not yet responded to Musk but is sure to be asked about the comments. So far, the White House has handled the situation delicately.

According to US media reports, the White House is trying to justify Musk’s opposition as a response to the bill’s cuts to green energy subsidies, including tax credits for electric vehicles like Musk’s Tesla cars.

Meanwhile, Axios reported that another source of tension is Trump’s decision to withdraw the nomination of Jared Isaacman, a Musk ally, to be the head of NASA, the US space agency.

“We should cut more”

On Wednesday, in the halls of Congress, Trump’s allies were treading a similarly delicate path.

“The bill can be improved, but it’s not an abomination,” Senator Lindsey Graham, a leading figure within the Republican Party and a loyal Trump defender, told the BBC.

“Let’s pass this bill,” he said. “We can make additional spending cuts as needed, but I want to put some points on the board: get the tax cuts done, make them permanent, get money out, take care of the border. But [Musk] is right, we should cut more.” Meanwhile, House Speaker Mike Johnson reportedly responded to Musk’s criticism of the bill in a closed-door meeting with Republicans. He also sought to reassure members about the billionaire’s threats to expel the bill’s supporters, according to Politico. A Tougher Task On Tuesday, White House press secretary Karoline Leavitt said Trump “already knows” Musk’s views on the legislation. “This is a great, beautiful project, and he stands by it,” she added.

Trump may support the legislation, but his task of convincing Senate Republicans to pass it will be even more difficult in the face of opposition from Musk.

His criticism could embolden Senate Republican budget hardliners who were already voicing concerns about how Trump’s bill will increase the federal deficit by billions of dollars over the next decade.

Several, including Rand Paul of Kentucky, Mike Lee of Utah, and Ron Johnson of Wisconsin, have said they may not vote for the House legislation unless it undergoes significant changes.

If those hardliners succeed in their goal and secure new spending cuts to popular social programs, centrist Republicans, such as Sens. Lisa Murkowski of Alaska and Susan Collins of Maine, will likely will revolt.

That's important because, assuming unified opposition from Democrats in the Senate, Republicans can only afford to lose just 3 of 53 Republicans if they want Trump's bill to pass.

Murkowski did not comment on the potential impact of Musk's comments on Wednesday, but told the BBC that he is “an influencer and his words have an impact.”

A Powder Keg

Freed from the constraints of his government job, Musk threw a powder keg into the delicate deliberations to unite the various Republican factions behind some kind of agreement. And it’s not the first time he’s done so.

His criticism sank a government spending bill last year by creating problems that took Republicans months to resolve.

Trump has said he wants the legislation on his desk to sign before Congress recesses on July 4. That could prove to be a difficult task, but he has an urgent deadline behind him.

His “big, beautiful bill” involves a $4 trillion increase in the borrowing limit on U.S. authority.

Treasury Department officials say that if that limit isn’t raised sometime in August, the country would face the prospect of defaulting on its unprecedented national debt.

Musk’s vocal opposition has been based, in part, on his warning that America’s mounting debt is becoming unsustainable. But if his criticism derails current efforts to pass the bill in Congress, it could hasten that day of financial reckoning.

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