The theory of American government is that official role, not blood relationship, determines who does what. If the president dies in office, he is succeeded by the vice president, not the first lady. There is no such role as “first daughter,” despite Ivanka Trump’s sometime use of that title. Yet at Hamburg, Ivanka posed with her father in group photographs with the chancellor of Germany, the prime minister of Canada, and other leaders—none of them joined by spouses or children.57
