Their fast-evolving political friendship has become a potential minefield, as Mr. Musk’s sprawling businesses may present conflicts of interest if Mr. Trump is elected in November.In a live-streamed conversation on X with former President Donald J. Trump last month, Elon Musk raised the idea of a “government efficiency commission.” Such a council could ensure that taxpayers’ money was “spent in a good way,” Mr. Musk said during their more-than-two-hour talk. “I’d love it,” Mr. Trump replied. On Thursday, Mr. Trump followed up on Mr. Musk’s suggestion. In a speech at the Economic Club of New York, Mr. Trump said he...