ary D. Cohn, President Trump’s top economic adviser, plans to resign, becoming the latest in a series of high-profile departures from the Trump administration, White House officials said on Tuesday. The officials insisted there was no single factor behind the departure of Mr. Cohn, who heads the National Economic Council. But his decision to leave came after he seemed poised to lose an internal struggle amid a Wild West-style process over Mr. Trump’s plan to impose large tariffs on steel and aluminum imports. “Gary has been my chief economic adviser and did a superb job in driving our agenda, helping...