Elon Musk’s bitter falling-out with President Trump could be costly for Tesla. As long as he is persona non grata in the Trump administration, Mr. Musk, the chief executive of Tesla, will struggle to persuade Republicans not to gut climate policies worth billions of dollars to the electric car and battery company.

Elon Musk and Donald Trump hurled insults at each other all day on Thursday after the president’s former ally attacked the bill containing his entire legislative agenda. And though Musk had somewhat backed off his hardline stance a few hours later,