Here’s How the Process of Impeachment Actually Works—And What Happened Last Time the U.S. Went Down That Road

Three presidents and countless scandals later, the impeachment of President Bill Clinton on Dec. 19, 1998, may seem like a relic of a different time. But, with the House of Representatives pursuing an impeachment inquiry against President Trump, that moment in time looms large.

Two decades ago, Clinton became only the second president ever to be impeached when, in the wake of his affair with a 22-year-old White House intern, the House of Representatives formally accused him of perjury and obstruction of justice. The Senate acquitted Clinton two months later, but for the time being he faced the possibility of becoming the first president to be convicted and removed from office.Impeachment is the most extreme way a president or other official can be punished for bad behavior in office. However, as the process has played out in public so few times, how it actually works may be less well known.

To better understand impeachment, why it works the way it does and what happened to Clinton, TIME spoke with Michael Gerhardt, a University of North Carolina professor who specializes in constitutional law and has frequently served as an expert witness before Congress on constitutional conflicts.

What is impeachment?

In the United States, impeachment is the process by which federal officials, including the president and federal judges, can be prosecuted and removed from office. While elections are the conventional way of replacing a president or other official, impeachment is intended for situations in which wrongdoing is so severe that more immediate action is necessary.

The Constitution lays out three reasons officials can be impeached — “treason, bribery, or other high crimes and misdemeanors.”

While the first two accusations are relatively straightforward, “high crimes and misdemeanors” is considered to be a broad category — and the founders likely intended for it to be that way. Such crimes would be considered what Alexander Hamilton called “violations of the public trust” in the Federalist Papers, Gerhardt says. In such cases, the president might do something that “benefits [him] in some way but hurts the country in another,” Gerhardt says.

For instance, Clinton misled others about Monica Lewinsky to protect himself from public embarrassment, but in doing so also may have eroded trust in the presidency.

Things that can get an official impeached may not even be crimes, and not all crimes are necessarily impeachable, Gerhardt adds. And while impeachment uses some of the language of a criminal case — such as “conviction” and “trial” — the process is actually a political trial of a political person by their peers. As Gerhardt explains, impeachable offenses are “special kinds of crime only people in office could commit.”

Why did the framers include impeachment in the Constitution?

Impeachment originated in British law, but the framers included impeachment in the Constitution for their own particularly American reasons.

While British law at the time also used a process of impeachment to prosecute individuals for treason or “high crimes and misdemeanors,” in practice, the bar of lords could impeach all the King’s subjects — whether or not they were officials — for any reason. The framers of the American Constitution narrowed impeachment to only include only federal officials, including the president.

Gerhardt says that the framers used impeachment as a way to make certain that everyone, including the president, is subject to the Constitution. It thus functions as part of the system of checks and balances that ensures each branch of the government has the ability to temper the power of the others.

“They didn’t want to go back to a world where the king was immune to impeachment, or to where ordinary people could be impeached,” Gerhardt says.

What are the steps in an impeachment?

On Dec. 19, 1998, President Clinton was impeached by the House of Representatives. However, impeachment is only the first stage in the two-pronged process to remove a president or another federal official from office.

After the House votes to impeach, the Senate must then hold a trial to determine whether an official is “guilty” and should actually be removed from office. To start the impeachment process, an individual member of the House must request that impeachment proceedings begin, or the House itself could pass a resolution to launch the proceedings. The Speaker of the House would then refer the process to the House Judiciary Committee, which must then determine if there is enough grounds for the process to move forward. If the committee finds enough evidence, it would then draft “articles of impeachment” and vote on whether to bring the articles to the House floor.

The case for impeachment would then go before the rest of the House. If a simple majority votes to pass the articles of impeachment, the President or other official is impeached.

After that, a two-thirds majority of the Senate must decide whether an official is guilty or not guilty of the charges in the articles of impeachment. For most officials, the President pro tempore of the Senate would oversee the process — but if the president were the official being tried, the Chief Justice of the Supreme Court would preside. If a two-thirds majority votes to convict, the official would be removed from public office. Afterward, the Senate could also vote to disqualify them from holding a federal office in the future and take away the official’s pension or other benefits. The convicted official could even face criminal or civil charges.

Read more: A Complete Timeline of Key Moments in the Clinton-Lewinsky Scandal

Why don’t impeachments happen more often?

Impeachments require a significant amount of political will, Gerhardt says. An impeachment will take up a lot of a Congress’s time and energy, and congress members who support impeachment have a lot to lose and potentially little to gain by undertaking an impeachment.

In practice, in order to actually remove a President from office, members of his or her own party must decide that there is enough public desire to impeach him or her, as Elaine Kamarck of the Brookings Institute has explained. “In order for an impeachment to move forward, a president’s own party has to get on board with an impeachment vote. For that to happen, it would mean that the president’s supporters in the electorate have lost faith in him,” she wrote.

In Clinton’s case, Senate Democrats ultimately decided not to convict, but it wasn’t always clear that they wouldn’t turn on him, Gerhardt says. “A lot of these people found that there was misconduct,” he says, “but there wasn’t enough to impeach him.”

Why was Clinton impeached?

The House voted to pass articles of impeachment on Dec. 19, 1998, on two charges: perjury and obstruction of justice. Prosecutors alleged that Clinton had perjured himself by testifying to investigators that he had not had “sexual relations” with Monica Lewinsky, and that he had attempted to encourage White House staff to give false testimony by denying the relationship.

Gerhardt said that, while popular support for impeachment waned as the proceedings went on, a significant undercurrent of public anger drove the proceedings forward.

“You don’t get an impeachment without a good deal of hate,” he says. “There were a lot of people who hated Bill Clinton.”

Why wasn’t Clinton convicted and removed from office?

Ultimately, there was uncertainty as to whether or not Clinton’s wrongdoing had been serious enough to justify removing him from office — as well as insufficient public support for doing so.

Bill Clinton’s approval ratings remained high throughout his second term of office, including during the trial. The impeachment seemed to galvanize the country to support him. His peak job-approval rating — 73% — was recorded the very week of the impeachment, according to Gallup. When Clinton and independent counsel Kenneth Starr were named Person of the Year in 1998, TIME columnist Michael Kinsley wrote that the lack of public interest in Clinton’s alleged misconduct was striking:

While many Senators thought that Clinton’s behavior was wrong, many did not agree that it was worthy of a conviction.

“In voting to acquit the President, I do so with grave misgivings for I do not mean in any way to exonerate this man,” Senator Susan Collins of Maine said in announcing her decision.

What happened to Bill Clinton after the impeachment?

Although Clinton was never convicted, he arguably did not get away unscathed from the proceedings.

Clinton’s law licenses with the U.S. Supreme Court and the Arkansas bar were suspended, which prohibited him from practicing law after his time in office. After he was suspended from the Supreme Court Bar in 2001, he chose to resign his license rather than be permanently disbarred. Possibly the biggest consequence of Clinton’s impeachment, however, was the mark it left on his public record.

On Jan. 17, 2001, Gary Langer ABC News characterized how most Americans felt about Bill Clinton at the time: “You can’t trust him, he’s got weak morals and ethics — and he’s done a heck of a good job,” Langer wrote.