WASHINGTON — The congressional power to remove a president from office through impeachment is the ultimate check on the chief executive. No president has ever been forced from the White House that style, although Richard Nixon resigned rather than having to confront the near certainty that he would exist removed from office.

Congress derives the authorization from the Constitution. The term "impeachment" is usually used to hateful removing someone from office, but it actually refers only to the filing of formal charges. If the House impeaches, the Senate then holds a trial on those charges to decide whether the officer — a president or any other federal official — should be removed and barred from property federal role in the hereafter.

The Firm has impeached 19 people, mostly federal judges. Two presidents, Andrew Johnson and Nib Clinton, were impeached, but the Senate voted not to convict either of them. Nixon resigned after the Judiciary Committee approved three manufactures of impeachment but before the total Firm voted on them.

President Clinton walks to the podium to evangelize a short statement on the impeachment inquiry in the Rose Garden of the White House on December. 11, 1998. J. Scott Applewhite / AP file

The Constitution provides that a president can exist impeached for "treason, blackmail, or other high crimes and misdemeanors." Treason and bribery are well understood, but the Constitution does non define "high crimes and misdemeanors."

Congress has identified iii types of conduct that constitute grounds for impeachment, including misusing an part for financial gain. Just the misdeeds need non be crimes. A president tin exist impeached for abusing the powers of the function or for interim in a manner considered incompatible with the office.

When Gerald Ford was a member of the House, he divers an impeachable offense as "any a majority of the House of Representatives considers it to be at a given moment in history." In other words, impeachment and conviction by Congress is a political penalization, not a criminal one.

1. What constitutes an impeachable law-breaking?

The founders intentionally kept the term "loftier crimes and misdemeanors" vague, because impeachment is meant to be a political act, not a legal one. Unlike in criminal law, there are no clear rules for evaluating when a president has stepped over the constitutional line.

The founders rejected the term "maladministration" as grounds for impeachment. They didn't want a president tossed out only considering Congress didn't think he was doing a adept chore. Alexander Hamilton said impeachable offenses were those that involved corruption of public trust. The term is generally understood to mean corruption of part that results in harm to the public.

The House impeached Andrew Johnson in 1868 during a fight over reconstruction after the Ceremonious War. Most of the articles of impeachment accused him of violating a federal law, since repealed, that said a president could not remove certain officials without Senate approval.

President Richard Nixon announces that he will not let his legal counsel, John Dean, to testify on Capitol Hill on the Watergate investigation in 1973. Charlie Tasnadi / AP file

The House Judiciary Committee canonical three articles of impeachment against Nixon in 1974, charging him with:

  • Obstruction of justice, for impeding the investigation into the break-in at Democratic National Committee headquarters in the Watergate office building;
  • Abuse of power, for trying to apply the CIA, FBI and other agencies to comprehend upwardly the Watergate conspiracy; and
  • Antipathy of Congress, for refusing to turn over cloth in response to congressional subpoenas.

The House approved ii articles of impeachment against President Bill Clinton in 1998, charging him with:

  • Lying under oath to a g jury virtually the nature of his relationships with Monica Lewinsky and Paula Jones; and
  • Obstruction of justice, for encouraging Lewinsky and others to brand false statements and concealing gifts he had given her.

2. How is the Trump investigation different from what happened with Clinton?

Three committees in the House — Intelligence, Oversight and Foreign Diplomacy — are conducting investigations, gathering documents and calling witnesses in the inquiry into Trump. In the Clinton impeachment, one commission, the House Judiciary, relied heavily on a report compiled by Kenneth Starr, the independent counsel who led the investigation, that listed 11 possible grounds for impeachment in four categories — perjury, obstruction of justice, witness tampering and corruption of power.

Business firm Speaker Nancy Pelosi, D-Calif., has said that while the Intelligence Commission will have the atomic number 82 in investigating Trump, the actual vote on specific articles of impeachment will be conducted past the Judiciary Committee and could draw on the conclusions of other House committees, too, though that seems unlikely. The process of voting on the articles, known as the committee mark-upwardly, volition exist televised and will likely take identify over several days.

House Judiciary took six days to recommend articles of impeachment against Nixon in July 1974 and three days to recommend articles of impeachment against Clinton in December 1998.

If approved by a simple bulk, the manufactures are reported to the full House and are privileged, meaning they tin can come up for immediate consideration, including potentially several days of debate. The president is impeached if the House approves any of the articles of impeachment by a simple bulk vote. The Firm and so appoints members to serve as "managers," or prosecutors, for the Senate trial.

3. Must the House laissez passer a resolution to officially launch an impeachment investigation?

The Constitution imposes no such requirement, and Business firm rules don't either, even though authorizing resolutions were passed in each of the three previous presidential impeachments.

Rep. Peter Rodino, D-Due north.J., who was chairman of House Judiciary in 1974 during the Nixon case, called passing a resolution "a necessary step." Business firm rules does not identify jurisdiction over impeachment in any specific commission, and Rodino said that in past impeachments the House had passed a resolution to give the investigating committee subpoena power. But the electric current Business firm leadership has said that such a resolution isn't needed, because the relevant committees already accept the necessary subpoena and staffing say-so.

Chairman of the House Judiciary Commission Peter Rodino reads his opening statement during an impeachment hearing against President Richard Nixon on May 9, 1974. Bettmann Archive via Getty Images

White House counsel Pat Cipollone is correct in saying that the Business firm "has never attempted to launch an impeachment inquiry against the president without a majority of the House taking political accountability for that decision" by passing a resolution.

Simply such a vote is not required. The House has voted to impeach federal judges without passing a resolution to qualify an investigation, and the Firm procedure for impeaching judges and presidents is the same. Notwithstanding, Firm Democrats volition concord a vote Thursday to clarify the rules for public hearings, even though a federal judge said on Oct. 25 that "a Firm resolution has never, in fact, been required to begin an impeachment inquiry."

iv. Would passing a resolution requite Congress authorization to get grand jury fabric, such as bear witness gathered during the Robert Mueller investigation?

Not necessarily. A fight over this upshot is now in federal court, and the Business firm won the showtime circular.

The House leans on what happened in 1974. After a federal grand jury in Washington finished an investigation of the Watergate scandal, it prepared a special study on its findings and recommended that its work exist forwarded to the House Judiciary Committee, which had begun impeachment proceedings.

Estimate John Sirica ruled that while the m jury's work was hush-hush, he had the authorization to release the material to the House. He said that the normal reasons for keeping g jury proceedings secret — such as preventing the escape of someone who might be indicted or insulating the grand jury from outside influence — no longer applied once the m jury's work was done. And he noted that Nixon did not object to letting the House committee get the textile. That's an important fact.

A federal appeals court agreed with Sirica's decision, and the grand jury material was turned over to the House.

Since then, the federal courts have narrowed the ability of judges to declare exceptions to grand jury secrecy. Earlier this year, for instance, the D.C. Excursion Court of Appeals said in a different case that in that location'southward no exception allowing historians to get admission. The court said it interpreted what Sirica did in Watergate as allowed under a federal rule that allows giving thou jury cloth to the House for "judicial proceedings." Merely that was said in a footnote: Information technology was non the holding in the instance, and that comment did not make whatever new police.

The Justice Section'due south view is that the effect isn't settled. It said in a recent filing in the current lawsuit that no court has ever squarely decided whether a House impeachment proceeding qualifies as an exception to longstanding rules of grand jury secrecy. And if Trump — different Nixon — explicitly objects to turning the material over, that could be a decisive factor.

In late October, Federal District Court Gauge Beryl Howell ordered the Justice Department to give the House Judiciary Committee an unredacted version of the Mueller report, along with some underlying materials. She ended that the requirement for preserving thou jury secrecy was outweighed by the House Judiciary Committee'due south demand for the fabric in its impeachment investigation. The Justice Department immediately appealed.

5. Do the president's lawyers go to participate in the House impeachment hearings?

This betoken is sometimes misunderstood. After the White House counsel complained that no Trump lawyers have been allowed to take part in the House committee sessions, many commentators said that the criticism was misplaced, considering Trump'due south lawyers would go their chance in the Senate trial, non in the House proceeding. Simply that's not how it has worked earlier.

White House Counsels Bruce Lindsey, left, and Charles Ruff depart the White Business firm with President Bill Clinton's personal attorneys Nicole Seligman and David Kendall, right, on Feb. 12, 1999. Khue Bui / AP file

In both the Nixon and Clinton proceedings, lawyers for the president were involved in the House impeachment process. In 1974, the Judiciary Commission gave Nixon's lawyers copies of documents and evidence, allowed them to sit down in on all hearings, including those in executive session, and permitted them to question witnesses who testified before the commission. Clinton'southward lawyers were also allowed to present witnesses and to briefly question Starr, the independent counsel whose report formed the backbone of the case for impeachment.

In the current proceedings, the House Judiciary Commission recently adopted a rule assuasive the president's lawyers to respond to evidence and testimony in writing. But there is no requirement for such an accommodation to the president's lawyers, and there was no such organisation when the House impeached Andrew Johnson.

6. Must the Senate hold a trial, or can it simply sit on the House articles of impeachment?

The Constitution only says the Senate has "the sole ability to try all impeachments," and some scholars have suggested this means the Senate is empowered but not required to carry out this role. But Senate rules suggest that it's a duty, not an option. Note the word "shall" in Senate Impeachment Rule One:

"Whensoever the Senate shall receive notice from the Business firm of Representatives that managers are appointed on their part to conduct an impeachment against whatever person and are directed to carry manufactures of impeachment to the Senate, the Secretarial assistant of the Senate shall immediately inform the House of Representatives that the Senate is ready to receive the managers for the purpose of exhibiting such articles of impeachment, approvingly to such notice."

In whatever event, Senate Majority Leader Mitch McConnell, R-Ky., has said: "Under the impeachment rules of the Senate, we'll accept the affair upward. ... We intend to do our constitutional responsibility."

7. How does a Senate trial piece of work?

The Constitution lays out but 3 requirements: The primary justice presides over the Senate trial of a president (but not the trial of any other official); each senator must be sworn (similar to the manner jurors take an adjuration); and a two-thirds vote is required to captive on any article of impeachment.

Once the preliminaries are out of the fashion, the trial takes place under procedures like to courtrooms. The House managers make an opening statement, followed by a argument from lawyers for the president.

During impeachments of judges, the evidence is generally presented during committee hearings at which the House managers call their witnesses, who tin be cantankerous-examined. And and then the reverse happens, with the president's counsel calling witnesses who tin be cross-examined by the House managers. The Senate has yet to make up one's mind whether, if Trump is impeached, witnesses volition be immune to testify to the full Senate.

Reporters listen to Monica Lewinsky's testimony during the Senate impeachment trial of President Bill Clinton in 1999. David Hume Kennerly / Getty Images file

There'southward no requirement for the president to announced, and he cannot be compelled to prove.

Like jurors in a trial, senators sit and listen. The rules say if they have questions, they tin can submit them in writing to exist asked by the main justice.

After both sides make their closing arguments, the Senate begins deliberations, traditionally in closed session. The Senate and then votes separately on each article of impeachment, which must accept place in open session.

8. What is the role of the primary justice?

It'southward express. The Senate has not adopted rules of evidence, only the rules requite the primary justice the authority to determine on all evidentiary questions. He tin can also put the questions to the full Senate for a vote on admissibility. Chief Justice William Rehnquist, who presided over the Clinton impeachment, quoted from Gilbert and Sullivan in responding to a letter inquiring well-nigh his time as presiding officer: "I did nothing in item, and I did information technology very well."

9. Could the president pardon himself if he's impeached?

No. The aforementioned constitutional provision that gives the president the ability "to grant reprieves and pardons for offenses against the United States" adds this phrase: "except in cases of impeachment."

ten. What would happen if the Senate bedevilled Trump?

He would be immediately removed from office, triggering the 25th Subpoena. Vice President Mike Pence would become president.

U.S. President Donald Trump speaks to reporters as he arrives for a meeting at the Pentagon, accompanied by Vice President Mike Pence in Arlington, Virginia on Jan. 18, 2018. Carlos Barria / Reuters

That would create a vacancy in the office of vice president, and then Pence would nominate someone to succeed him, who would become vice president upon confirmation by both houses of Congress.

This is the procedure followed when Nixon resigned. Ford, the vice president, became president and nominated equally vice president former New York Gov. Nelson Rockefeller, who was confirmed afterwards extensive congressional hearings.

Pete Williams is an NBC News correspondent who covers the Justice Department and the Supreme Court, based in Washington.

Alex Moe is a Capitol Hill producer for NBC News covering the Business firm of Representatives.

Frank Thorp V is a producer and off-air reporter covering Congress for NBC News, managing coverage of the Senate.