The relationship between Mr. Trump and tech industry power brokers was built on money and the promise of deregulation, with Mr. Musk in the middle of it all.

Cracks in Silicon Valley and Washington’s marriage of convenience had been appearing for weeks, particularly over the Trump tax bill that so irked Musk. Deficit hawks balked at the legislation adding trillions to the US debt pile, while more socially progressive tech figures bridled at proposed cuts to entitlement programmes like Medicaid.

As Elon Musk and US president Trump spar on social media, tech investors and executives are being forced to choose whether to support the most powerful man in business—or the White House.