The announcement by House Speaker Nancy Pelosi that the House “is moving forward with an official impeachment inquiry” against President Donald Trump because she believes his actions “have seriously violated the Constitution” kicks off a complex and consequential process.

But what exactly is impeachment? How hard would it be to impeach the president and remove him from office?

The average American understandably isn’t an expert on impeachment. Only two presidents have been impeached by the House – Andrew Johnson in 1868 and Bill Clinton in 1999. But neither man lost his job.

Impeachment is complicated and takes time. Parliamentary democracies can quickly remove a prime minister when a majority of lawmakers cast a vote of no-confidence in the leader. But in the U.S., the impeachment process is much tougher.

What is impeachment?

Impeachment has nothing to do with criminal prosecutions carried out by the Justice Department for violations of federal law, although such criminal violations may form a basis for impeachment.

Impeachment is the process set out in Article II, Section 4 of the Constitution for Congress to remove from office the president, vice president and “all civil Officers of the United States” for “Treason, Bribery or other high Crimes and Misdemeanors.”

Under Article I, Section 2 of the Constitution, the House of Representatives has the “sole Power of Impeachment.”

In other words, only the House can pass a resolution of impeachment alleging a president has committed “high crimes and misdemeanors.” Such a resolution, which requires a simple majority vote, is similar to a criminal indictment by a grand jury – it is an unproven list of charges that a president has engaged in actions warranting impeachment.

If the House passes an impeachment resolution, the process moves to the Senate. Under Article I, Section 3 of the Constitution, the Senate has “sole Power to try all impeachments.”

The Senate becomes a trial court with all senators sitting as judge and jury. Based on historic practice, members of the House can act as prosecutors.

It is important to note it is entirely up to the Senate to decide whether to hold a trial. There is no obligation under the Constitution to do so.

This means that even if the Democratic majority in the House votes to impeach Trump, the Republican majority in the Senate could decide to not even consider removing him from office.

House Democrats opposed to impeaching Trump say there’s no point in passing an impeachment resolution because it would likely be dead on arrival in the Senate.

How does an

impeachment trial work?

If the Senate decides to hold a trial, the Constitution says the chief justice of the Supreme Court shall preside over the proceeding. It takes a vote of “two-thirds of the Members present” in the Senate to convict any federal officer subject to an impeachment charge.

The two-thirds vote to convict means 67 votes are needed in the 100-member Senate to remove the president and other federal officers from office. That’s a very high hurdle, probably impossible to leap in Trump’s case.

Democrats and independents allied with them hold only 47 seats in the Senate – meaning that even if they all voted to convict Trump, they also need the votes of 20 Republicans. Not a single GOP senator has called for Trump to be impeached so far, and the chances of 20 jumping on the impeachment bandwagon are slim.

If a federal officer is convicted by the Senate, it is not a criminal conviction. The Constitution states impeachment “shall not extend further than to removal from Office, and disqualification to hold and enjoy any Office of honor, Trust or Profit under the United States.”

In other words, a federal official can be removed from office. He or she can also be banned from holding any other federal office in the future.

What happens when

an official is removed?

On the other hand, conviction does not bar the removed official from being “liable and subject to Indictment, Trial, Judgment and Punishment, according to Law.”

A federal official who is impeached, convicted and removed from office can then be criminally prosecuted if he has violated a federal law, such as accepting bribes or engaging in treason.

How is impeachment

different from other trials?

The most important point to understand about impeachment is that it is not a legal proceeding like a federal criminal prosecution. Formal procedural or evidentiary rules that apply to criminal and civil trials in federal courts are not applicable in an impeachment trial.

Other than the constitutional division of labor between House and Senate, the directive that the chief justice presides when it is the president being impeached and the requirement of a two-thirds vote to convict, it is entirely up to the House and Senate to set rules for how to proceed with impeachment.

It is also entirely up to Congress to determine what it considers “Treason, Bribery or other high Crimes and Misdemeanors” that constitute grounds for impeachment.

The Supreme Court – in the 1993 case Nixon v. United States (involving a federal judge named Nixon, not former President Richard Nixon) – held the impeachment process is a political question. It is not an issue reviewable by or within the jurisdiction of federal courts.

How has impeachment

been used in the past?

Historically, the House has impeached 19 federal officials: 15 judges, one cabinet member, one U.S. senator and Presidents Andrew Johnson and Bill Clinton.

Many people mistakenly believe Nixon was impeached. In fact, Nixon resigned after the House Judiciary Committee recommended impeachment but before the House could vote on a resolution of impeachment.

Both Johnson and Clinton were acquitted in their Senate impeachment trials. Of the 14 other impeachment trials, eight resulted in convictions (all federal judges).

What is an

impeachable offense?

Impeachment is probably not limited to criminal acts.

Treason and bribery are clearly criminal violations, but the Constitution does not define “high Crimes and Misdemeanors.” Alexander Hamilton argued that impeachable offenses would include “the misconduct of public men” or the “abuse or violation of some public trust.”

Both houses of Congress have in the past given the phrase “high Crimes and Misdemeanors” a broad reading.

Is impeachment

about law or politics?

Impeachment is primarily a political process.

If a majority of Americans do not believe impeachment of a president is warranted because no actual wrongdoing occurred (or the alleged wrongdoing is not sufficiently serious), there’s little doubt members of Congress pushing impeachment will be unsuccessful and may suffer damaging political consequences at the ballot box.

After Republicans tried and failed to remove Clinton, they lost seats in Congress in the next election. Democratic opponents of impeaching Trump fear this could happen to them if they impeach him.

The impeachment process was not placed in the Constitution so it could be used for partisan gamesmanship but to remedy serious misbehavior.

If members of Congress start voting to impeach a president because they simply oppose his policies, we could see a lot more attempts to impeach presidents in the future.

Congress should be wary of abusing the impeachment authority in such a manner, because it could imperil the stability of our constitutional structure by removing a duly elected president.

Whether you are a Republican or Democrat, and whether you support or oppose Trump, you should oppose making impeachment a frequently used move against presidents. Someday, a president you think is doing a great job could be targeted.

Hans von Spakovsky is a senior legal fellow at The Heritage Foundation.