The truce between Elon Musk and US President Donald Trump didn’t even last a month.

After the Senate narrowly passed a procedural vote to debate Trump’s “Big, Beautiful Bill” over the weekend, Musk on Monday said he would use his vast resources to launch primary campaigns against Republicans in Congress who voted for the massive domestic policy agenda. Musk spent much of Monday and early Tuesday morning posting and re-posting messages that criticise the tax cut and spending bill — particularly for its sky-high cost.

Trump late on Monday night fought back, suggesting his administration may investigate Musk’s companies’ massive government subsidies.

So far, the feud hasn’t grown as personal or as vicious as their public blow-up last month when Musk, without providing evidence, accused Trump of withholding information about disgraced financier and convicted paedophile Jeffrey Epstein, and claiming that Trump’s name was included in the government’s so-called Epstein files.

A week after the peak of that feud, Musk said he regretted some of his posts about Trump. Musk deleted some of his most inflammatory X posts, including the one relating to Epstein and another agreeing with the suggestion that Trump should be impeached. Musk had since softened his tone about Trump and the bill, largely shifting his focus on social media and in interviews to his companies.

That shifted dramatically Monday when Musk began posting nonstop about his opposition to Trump’s signature legislation. But this time around — at least so far — Musk hasn’t mentioned Trump’s name in his dozens of posts about the bill.

Still, the fight is costing Musk where it counts: Tesla’s (TSLA) stock tumbled nearly 5 per cent in premarket trading Tuesday after losing 2 per cent on Monday, missing out on the broader stock market gains that sent the S&P 500 and Nasdaq to record highs. Much of Musk’s wealth is tied up in Tesla’s publicly traded stock.

Tesla shareholders have been very sensitive to the Musk-Trump spat, nervous that Trump may make good on his threat to dissolve contracts with SpaceX or Tesla. The stock lost about 14 per cent on June 4, the day when Musk and Trump’s feud over the spending bill erupted into the public.

“This BFF situation has now turned into a soap opera that remains an overhang on Tesla’s stock with investors fearing that the Trump Administration will be more hawkish and show scrutiny around Musk-related US government spending,” said Dan Ives, analyst at Wedbush Securities, in a note to investors on Tuesday. “Tesla investors want Musk to focus on driving Tesla and stop this political angle.”

Musk’s renewed attacks on the bill started on Monday afternoon, when he threatened members of Congress who voted for the legislation. He said the bill would undermine his efforts at the Department of Government Efficiency, which sought fiscal responsibility by eliminating what he and others viewed as wasteful spending.

But the Senate bill would add nearly $US3.3 trillion ($5 trillion) to the deficit over the next decade, according to a Congressional Budget Office estimate released Sunday. The Senate legislation costs more than the House-approved bill, which would add $US2.4 trillion ($3.65 trillion) to the deficit over the next decade.

The White House has argued the bill “slashes deficits” and the debt, while “unleashing economic growth”. Musk wasn’t having it.

“Every member of Congress who campaigned on reducing government spending and then immediately voted for the biggest debt increase in history should hang their head in shame! And they will lose their primary next year if it is the last thing I do on this Earth,” he wrote on X.

He later shared a campaign poster with “LIAR” written across Pinocchio’s face above the text “Voted to increase America’s debt by $5,000,000,000,000”.

“Anyone who campaigned on the PROMISE of REDUCING SPENDING, but continues to vote on the BIGGEST DEBT ceiling increase in HISTORY will see their face on this poster in the primary next year,” Musk wrote.

Musk wrote several posts about creating a third party called “the America Party”, which would serve as a populist alternative to the Republican and Democratic parties.

“If this insane spending bill passes, the America Party will be formed the next day,” Musk said.

He also posted that he would contribute to the re-election campaign for Kentucky Rep. Thomas Massie, who has been one of the few Republican voices in Congress to take a stand against the bill. Trump has publicly scolded Massie for his opposition.

Trump early on Tuesday morning responded with a threat: He could use DOGE, which Musk once led, to probe the government contracts and subsidies Musk’s companies receive.

“Elon may get more subsidy than any human being in history, by far, and without subsidies, Elon would probably have to close up shop and head back home to South Africa,” Trump wrote on Truth Social. “No more Rocket launches, Satellites, or Electric Car Production, and our Country would save a FORTUNE. Perhaps we should have DOGE take a good, hard, look at this? BIG MONEY TO BE SAVED!!!”

Trump made a similar suggestion last month. Although it’s not clear that Trump would follow through, Musk’s companies are reliant on the federal government as a major source of revenue. And Tesla, SpaceX and Musk’s other companies, including social media platform X, artificial intelligence company xAI and brain-computer interface company Neuralink all face regulation from the federal government.

Unlike SpaceX, which makes the bulk of its money from the government, Tesla has relatively few government contracts. But numerous federal policies directly affect Tesla’s finances, including a $7500 tax credit for electric vehicle buyers that allows Tesla and other automakers to raise prices. The tax credit has also has helped boost EV sales. That was likely worth billions to Tesla last year alone.

Tesla also reported more than $8 billion in sales over six years of regulatory credits to other automakers to help them comply with federal and state emission standards. Trump is in favor of rolling back those standards and stripping states of the power to set their own emissions rules, which would destroy the market for those credit sales.

The loss of the EV tax credit could cost Tesla $1.2 billion a year and the loss of regulatory credit sales another $2 billion, according to JPMorgan.

“At the end of the day being on Trump’s bad side will not turn out well, and Musk knows this,” Ives wrote.

Trump has argued that Musk’s primary opposition to the Big, Beautiful Bill is the loss of EV tax credits. Musk denies that, retweeting a post Monday that said, “Elon’s opposition to the ‘One Big Beautiful Bill’ has never been about its removal of EV tax credits or the EV mandate, it’s simply about his passionate opposition to rising government debt.”

“All I’m asking is that we don’t bankrupt America,” Musk posted.

It’s unclear whether Musk’s threats will kill the bill’s chances. Trump has mounted a massive pressure campaign on holdouts, putting members of Congress in a difficult position of choosing Musk and his war chest of cash over Trump and his bully pulpit.

Musk spent more than $275 million to support Trump and other Republican candidates in the 2024 election. According to Federal Election Commission filings, Musk’s political action committee, America PAC, last gave money in March to support two Republican candidates running in special elections in Florida — Randy Fine and Jimmy Patronis. In late May he said in an interview he was planning to cut back on political spending, saying he has “done enough.”

But Musk has the resources to make good on his promises to support a slate of alternate candidates if he chooses.

That doesn’t guarantee he’ll succeed: Musk spent considerable time and resources in a losing effort to elect a Republican to Wisconsin’s supreme court earlier this year. His popularity remains low, and, ultimately, Donald Trump is president, and Musk is not.