Throughout American history, business leaders have been able to assume that an American president of either party would uphold the rule of law, defend property rights and respect the independence of the courts. Implicit in that assumption is a fundamental belief that the country’s ethos meant their enterprises and the U.S. economy could thrive, no matter who won. They could keep their distance from the rough-and-tumble of campaign politics. No matter who won, they could pursue long-term plans and investments with confidence in America’s political stability. In this election, American business leaders cannot afford to stand passive and silent. Donald...