Former President Donald Trump said he’d support cutting the corporate tax rate to 15% from its current level of 21%, a move Sen. JD Vance said he opposed two months ago before he became Trump’s running mate. That difference reflects the difficulties in reconciling their ideologies, giving corporate America a bit of whiplash. The Ohio Republican has fashioned an image as an economic populist willing to confront Wall Street and other industry titans, which has unnerved some...