Late last month, Nikki Haley, the former U.S. ambassador to the United Nations, got an unexpected call from Jamie Dimon, CEO of JPMorgan Chase. Dimon said he was impressed by Haley’s knowledge of policy details and her open-minded approach to complex issues raised in the Republican presidential race, according to a person familiar with what they discussed. Keep it up, he told her. He wasn’t the only business heavyweight to say so. In recent weeks, a group of CEOs, hedge fund investors and corpor