WASHINGTON (AP) -- Maybe it was always going to end this way, with two billionaires angrily posting about each other on social media, fingers flying across pocket-sized screens as their incandescent feud burned hotter by the minute.

But even if the finale was predictable, that didn't make it any less shocking. After long months when Donald Trump and Elon Musk appeared united in their chaotic mission to remake Washington, their relationship imploded this week like a star going supernova.

It began with Musk complaining about the centerpiece of Trump's legislative agenda, which the president at first took in stride. Eventually Trump let slip that he was disappointed in his former adviser, prompting Musk to unleash a flood of insults and taunts.

He accused Trump of betraying promises to cut federal spending, shared a suggestion that the president should be impeached and claimed without evidence that the government was concealing information about his association with infamous pedophile Jeffrey Epstein. Perhaps most viciously, Musk insisted that Trump wouldn't have won last year's election without his help.

Trump, not one to slouch from a fight, could hold back no longer. He posted that Musk had been "wearing thin," that he had "asked him to leave" his administration, that the tech titan had "gone CRAZY."

Maybe, Trump threatened, he should save taxpayer money by canceling government contracts and subsidies for Musk's companies.

On and on it went, as liberals savored the spectacle of their most despised political opponents clawing at each other's digital throats and conservatives reeled at the prospect of having to pick sides. Laura Loomer, a right-wing provocateur and conspiracy theorist, saw an opportunity to position herself as the voice of reason.

"This fight should be taken offline," she said -- on social media, of course.

The question now is whether Trump and Musk find some way to step back from a battle that is tearing apart one of the most consequential relationships in modern American politics. If they don't, there's little telling how far the fallout could spread from a collision between the world's most powerful man and its wealthiest.

At stake are the future of Musk's companies, including electric automaker Tesla and rocket manufacturer SpaceX; government programs that rely on the billionaire entrepreneur's technology; legislation for advancing tax cuts and Trump's other priorities in Congress; Republican chances in next year's midterm elections; and an entire political ecosystem that has orbited around Trump and Musk's deteriorating partnership.

"It's like India and Pakistan," said Republican Rep. Ryan Zinke of Montana, referring to two nuclear-armed nations that recently skirmished along their border. "It just escalates and neither one of them seem to back down and understand the strength of each other."

Trump and Musk were always an odd pairing, with contrasting world views and deep generational and stylistic differences.

Trump, 78, comes from old-school New York real estate and never appears in public without a suit and tie unless he's on the golf course. Before running for president, he became a household name as a reality television star.

Musk, 53, is an immigrant from South Africa who struck it rich in Silicon Valley. In addition to running Tesla and SpaceX, Musk owns the social media company X. He's fashioned himself as a black-clad internet edgelord, and his wealth vastly outstrips Trump's.

But Trump and Musk are kindred spirits in other ways. They're experts at generating attention who enjoy stirring the pot by riling up their opponents. Each has sought more power to accomplish existential quests. Trump assails the federal "deep state" that resisted him during his first term, while Musk warns about the country going bankrupt from excessive spending and promotes an interplanetary future powered by his rocket technology.

Musk endorsed Trump after the Republican candidate was nearly assassinated in Butler, Pennsylvania, and he began spending millions to support him. His social media megaphone was a powerful addition to Trump's comeback campaign, magnifying his efforts to court tech leaders and young, very online men.

Trump rarely tolerates sharing the spotlight, but he seemed enamored with his powerful backer, mentioning him in stump speeches and welcoming him onstage at rallies.

After the election, Musk was a fixture around Mar-a-Lago, posing for photos with Trump's family, joining them for dinner, sitting in on meetings. Instead of growing tired of his "first buddy," Trump made plans to bring Musk along to Washington, appointing him to lead a cost-cutting initiative known as the Department of Government Efficiency.

Musk tried to establish himself as the president's omniscient and omnipresent adviser. He held court in Cabinet meetings, slept over in the Lincoln Bedroom and helped himself to caramel ice cream from the White House kitchen.

The federal bureaucracy practically trembled before Musk, who oversaw layoffs and downsizing with his team of acolytes and engineers embedded in various agencies.

Musk appeared thrilled at his opportunity to tinker with the government and exulted in his bromance with Trump, posting on Feb. 7 that he loved the president "as much as a straight man can love another man."

Trump returned the favor on March 11, allowing Musk to line up Tesla vehicles on the White House driveway as his company was struggling with declining sales. Trump made a show of choosing a cherry red electric car for himself.

But cracks were emerging, especially as Trump pursued tariffs that could raise costs for Musk's businesses. Musk said Peter Navarro, the president's trade adviser, was "truly a moron" and "dumber than a sack of bricks" on April 8.

The billionaire entrepreneur, who had never before worked in public service, seemed to be souring on government. He suggested there wasn't enough political will, either in Congress or in the White House, to adequately reduce spending.

Trump started signaling that it was time for him to leave even though Musk said he would be willing to stay.

Shortly before announcing his departure, Musk said he was "disappointed" by legislation that Trump called the "big beautiful bill" because it would increase the deficit. The measure includes tax cuts, more money for border security and changes to Medicaid that would leave fewer people with health insurance.

"I think a bill can be big or it could be beautiful," Musk said. "But I don't know if it could be both."

The criticism didn't prevent Trump from giving Musk a send-off in the Oval Office, where he presented his outgoing adviser with a ceremonial key.

"Elon is really not leaving," Trump said. "He's going to be back and forth."

Musk said, "I'll continue to be visiting here and be a friend and adviser to the president."

It's hard to imagine that now.

Musk escalated his attacks on the legislation Tuesday, calling it a "disgusting abomination," and Trump tried to fend off the criticism.

"He hasn't said bad about me personally, but I'm sure that will be next," the president said Thursday in the Oval Office during a meeting with the German chancellor.

It was.

Musk quickly took to X to vent his anger at Trump, saying his tariffs "will cause a recession in the second half of this year" and accusing him of lying. He also said it was "very unfair" that the legislation would eliminate tax incentives for electric vehicles.

Trump fired back in real time as he tried to maintain momentum for his legislation, which faces a difficult debate in the Senate.

"I don't mind Elon turning against me, but he should have done so months ago," the president posted. "This is one of the Greatest Bills ever presented to Congress."

Meanwhile, some of Trump's allies plotted revenge.

Steve Bannon, a former Trump adviser who hosts an influential conservative podcast, said the president should direct the U.S. government to seize SpaceX. He also encouraged Trump to investigate allegations that Musk uses drugs and "go through everything about his immigration status" in preparation for potential deportation.

"We'll see how good Elon Musk takes a little of that pressure," Bannon said, "because I happen to think a little of that pressure might be coming."

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Associated Press writers Tom Beaumont, Kevin Freking and Michelle L. Price contributed to this report.