WASHINGTON — Gary D. Cohn and Steven Mnuchin have spent months behind closed doors with Republican congressional leaders sketching the contours of an elaborate and politically difficult tax overhaul that is President Trump’s top priority.
Mr. Trump hopes to jump-start the process on Wednesday, traveling to Springfield, Mo., for a speech calling for large tax reductions and a long-anticipated revamping of the code. But he has largely left it to Mr. Cohn, the director of the National Economic Council, and Mr.