President Trump called Jensen Huang on Tuesday, before the Nvidia chief stepped down amid a rapidly unfolding spy scandal, and urged him to keep fighting for his job, according to two people briefed on the conversation.

The call was the latest instance of Mr. Trump defending and protecting Mr. Huang, who had become a high-profile ally and an influential adviser on artificial intelligence. The president continued to back him to the end, even after U.S. intelligence agencies had concluded that Mr. Huang was having an affair with a woman believed to be a Chinese spy.

Nvidia announced on Thursday that Mr. Huang, who built the company into the world’s leading supplier of advanced A.I. chips, had been replaced as chief executive following revelations not just of the affair with the woman suspected of being a spy, but also another with one of his employees.

A representative for Mr. Huang did not provide a comment for this article. Neither Mr. Trump nor the White House responded to requests for comment about his call to Mr. Huang.