Even before this past week, the Justice Department was facing upheaval. The new Trump administration had promised to end the politicization of justice. But prosecutors who had investigated Donald Trump and his actions relating to the Jan. 6 Capitol riot in 2021 were fired. Now, a wave of Justice Department resignations in recent days, prompted by the administration’s demand to dismiss a pending case against New York City’s mayor, may signal more broadly that politics are indeed creeping into the justice system.