Now that the House of Representatives has voted to impeach President Trump, action shifts to the Senate, whose members are charged by the Constitution to determine whether he should be convicted or acquitted. Yet wary Democrats are slow-walking the process in a bid to secure procedural guarantees from Senate Republicans on how the trial will unfold. The House must first appoint members who will manage its case during the trial. When that happens, the House can notify the Senate of its decision to impeach the president and appoint managers.According to Speaker Nancy Pelosi, D-Calif., the House will refrain from appointing...