Members of the American diplomatic corps testified about the state of U.S. foreign policy in private hearings on Capitol Hill this week. According to our national political correspondent, their testimonies revealed “a remarkably consistent story” about the ways in which career diplomats have been sidelined to make room for Trump administration officials. The conduct of those officials, and the nature of the directives they received, is at the center of the House impeachment investigation.We look back at a week inside the U.S. Capitol as that inquiry enters a pivotal phase. Guest: Nicholas Fandos, who covers Congress for The New York Times. For more information on today’s episode, visit nytimes.com/thedaily. Background coverage: Gordon D. Sondland, the U.S. ambassador to the European Union, told impeachment investigators on Thursday that President Trump delegated Ukraine policy to his personal lawyer Rudolph Giuliani.Mick Mulvaney, the acting White House chief of staff, threw Washington into turmoil on Thursday when he first confirmed, then retracted, that Mr. Trump had withheld military aid to pressure Ukraine.