By Matt Peterson

It wasn't difficult to predict an eventual end to the alliance between Elon Musk and President Donald Trump. But even if you saw it coming, the snarling dogfight unfolding between the two thin-skinned billionaires has been stunning to watch.

For all its popcorn appeal -- one of the mothers of Musk's many children who has sued him for sole custody told Trump to let her know if he needed "any breakup advice" -- the spat comes with urgent consequences. At stake in the fight is a multi-trillion-dollar tax bill, the fate of one of the world's largest companies, the future of America's dominant political party, and even the livelihood of a couple of U.S. astronauts.

The two men have disagreed on policy before, including the appeal of electric vehicles and the value of tariffs. But last summer, when an assassin's bullet bloodied Trump's ear, the tech mogul rushed out an endorsement that had been planned for later in the year. Trump's "strength under fire" was "incredibly inspiring," Musk said later. Musk went on to pour nearly $300 million into the presidential race, driving a get-out-the-vote effort in Pennsylvania that many saw as decisive in Trump's win.

Both men benefited. Musk was drawn into Trump's inner circle as the head of the U.S. DOGE Service, short for the Department of Government Efficiency, though it was never in fact a department. Tesla stock soared on the premise that the company would gain from its CEO's association with the president. Trump backed Musk to the hilt, going so far as to read off a price list of Musk's cars on the White House lawn and promising to buy one himself.

The White House didn't immediately respond when asked if Trump ever went through with the purchase.

Signs of disagreement came swiftly after Musk's service as a special government employee ended last month. Musk, in an interview with CBS that aired Sunday, criticized the tax bill Trump has championed. Trump shrugged off the criticism, but Musk wouldn't -- or couldn't -- let it go.

On Wednesday, the Congressional Budget Office issued a report detailing the bill's $2.4 trillion toll on the deficit. Musk began to unload, calling the bill a " disgusting abomination" and urging senators to kill it. Some eagerly joined in.

That was apparently too much for Trump. "I'd rather have him criticize me than the bill," he told reporters assembled for a joint press appearance with the newly elected chancellor of Germany, who sat by watching as Trump began to unload on his former ally, saying their once-great relationship looked to be over. Trump even dished that he had offered Musk makeup to cover the black eye he had when the two men stood together in the Oval Office just days earlier. (Once a reality star, always a reality star.)

That moment was enough to turn the dispute from a disagreement among friends into a political earthquake. "Without me, Trump would have lost the election, Dems would control the House and the Republicans would be 51-49 in the Senate," Musk posted on X. Trump responded on his social media network, Truth Social, threatening to end Musk's government "contracts and subsidies."

That the dispute unfolded on rival social networks wasn't lost on the shareholders in Trump Media, the owner of Truth Social. It has never turned a profit, and one theory among investors is that Musk might buy it and merge it with X. The fight dashed some of those hopes. Trump Media stock plummeted 8% on Thursday. Trump holds more than 40% of the stock in the name of his son Don Jr., meaning the fight has immediately wiped some $170 million off his net worth on paper.

Musk fared worse. Tesla closed down 14%, wiping out $150 billion in market capitalization from the company, and in the range of $30 billion off his wealth.

The costs mount from there. Senators want to avert a sharp rise in taxes at the end of the year if cuts set to expire aren't extended. They will now find themselves stuck between the world's richest man, who has often threatened to fund primaries against those who oppose him, and the president who remains overwhelmingly popular in his party and has amassed a $600 million midterm war chest, according to the Associated Press. A touchy bond market is likely to react quickly to changes in the bill, with the consequences spilling into stocks and other assets.

Musk has even threatened to form his own political party. While U.S. history is littered with the ill-remembered remains of third parties, Musk through X controls a megaphone that rivals even the White House's bully pulpit. Many Republicans are already nervous about their chances in 2026, and getting Musk on the wrong side of them won't help.

Even the astronauts on the International Space Station may be getting nervous. NASA has relied on Musk-owned SpaceX to get people and goods to and from the space station. Whether Trump was aware of that when he threatened Musk's contracts isn't clear, but Musk certainly is. SpaceX "will begin decommissioning" its spacecraft immediately, Musk said.

All this would be funny if not for the calamitous fallout it could have for ordinary people who just want the government to do the basics without any fuss. The two men seem incapable of seeing past their anger at each other.

A full accounting of the stakes would include Musk's cuts to U.S. agencies, which critics say have halted lifesaving aid in many developing countries. But the worries we can identify now are almost certainly just the tip of the iceberg.

The fight is unfolding in plain view of the leaders of dozens of countries with whom Trump is deep in negotiations over tariffs. That includes China's Xi Jinping, who drew a hard line with Trump in talks just this morning, refusing to do more than recommit to an existing tariff truce. And Russia's Vladimir Putin, who told Trump "very strongly" just yesterday that he intended to retaliate against Ukraine for its sneak attack on Russia's bomber fleet. If Trump can't control his own adviser, why should they expect him to hold up on his tariff threats?

The hallmark of Trump's second term has been its ideological consistency. Everyone who serves is devoted to Trump's mission, however they choose to define it in that moment. But that also means that no one can tap the president on the shoulder and tell him he's going too far. The same goes for Musk, who has achieved a level of otherworldly success. No one will be surprised if he really does blast off for Mars.

That might be the best anyone can hope for because, right now, one planet isn't big enough for the two men's egos.

Write to Matt Peterson at matt.peterson@dowjones.com

This content was created by Barron's, which is operated by Dow Jones & Co. Barron's is published independently from Dow Jones Newswires and The Wall Street Journal.

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June 05, 2025 18:30 ET (22:30 GMT)

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