The day after Hillary Clinton testified in front of the House Select Committee on Benghazi last October, John Podesta, the Democrat’s campaign chairman, met for dinner with a small group of well-connected friends, including Peter Kadzik, a top official at the Justice Department. The dinner arrangement, revealed in hacked Podesta emails released by WikiLeaks, is just the latest example of an apparent conflict of interest between the Clinton campaign and the federal agency charged with investigating the former secretary of state’s email practices. Podesta and Kadzik, the assistant attorney general for legislative affairs, were in frequent contact, other emails show....