Impeachment is not the same as removing the US president. A majority vote of the House of Representatives is required to impeach a president. But impeachment is only a first step towards removal from office. After impeachment, a trial in the Senate and guilty votes from a super-majority of two-thirds of the Senate is needed to convict and remove a president from office.
Impeachment is a political process, albeit with legal overtones. Critically, criminal acts are neither necessary nor sufficient for impeachment and conviction of a president.
No president has been convicted and removed from office. Just two presidents have been impeached by the House. Examination of the Nixon and Clinton impeachment proceedings highlight the intensely political nature of impeachments. Nixon resigned before the House of Representatives voted on impeachment. Clinton is just one of two presidents to be impeached and tried by the Senate; the other was Andrew Johnson (1868), whose trial in the Senate concluded with an acquittal, just one vote short of the two-thirds majority required for conviction. Neither Clinton nor Johnson were convicted. Resignation or death remain the only ways US presidents have left office prior to electoral defeat or term limits.
While based on only two recent cases, I tentatively venture that the following political logic structures presidential impeachment and trials. A president who thought it was likely that two-thirds of the Senate would vote for conviction would resign prior to impeachment or trial, perhaps even trading the timing and manner of their resignation for a presidential pardon from their successor, protecting them against criminal prosecution, a la Nixon. Conversely, a president confident of the result of a trial in the Senate will not resign, a la Clinton. If this logic is correct: (a) we ought to never observe a successful conviction and removal of a president from office; (b) equivalently, Senate trials of presidents — when they occur — do not result in convictions.
Divided government was an essential element of the Nixon and Clinton impeachment proceedings. Nixon, a Republican president, faced impeachment and trial with Democratic majorities in both the House and Senate. Nixon resigned in the face of crumbling support within his own party, making impeachment and conviction all but assured. Conversely, Clinton was impeached with Republican majorities in the House of Representatives and the Senate, but with near universal opposition to impeachment among Democratic House members. No Democratic senator voted for Clinton’s conviction in the Senate.
Trump’s approval numbers lie around the 40 per cent mark, low by historical standards for a president this early in his term, but not so low that Republicans will move against him. Critically, Trump’s support among Republican partisans remains extremely high, close to Democratic levels of support for Clinton through his impeachment and Senate trial.
Special Counsel Mueller — appointed to investigate ties between the Trump campaign and Russia — has less investigative scope and autonomy than did Kenneth Starr who served as independent counsel investigating a series of allegations against the Clintons and their associates. This suggests that the investigation into Trump — and the question about impeachment proceedings being pursued by the Congress — may be completed more expeditiously than either the Watergate investigation (1973-74) or the series of investigations by Starr (1993-1998).