By Tara Law
Updated: May 13, 2019 3:14 PM ET | Originally published: March 27, 2019

Impeaching an American President is rare. It’s only happened twice in American history — to Presidents Andrew Johnson and Bill Clinton — and neither of those times resulted in a president being removed from office. However, the question of impeachment once again looms large in some corners of American politics.

To be impeached, a President or other federal official must have committed one of the violations described by the Constitution as “treason, bribery, or other high crimes and misdemeanors.” But history shows that if a President is to be impeached, the biggest factor may be political will — whether members of a President’s own party are willing to turn against him, and whether enough members of Congress believe that trying to remove the President is worth the risk of losing popular support.

Impeachment alone isn’t the only step to take a President out of office, but is actually the first part of a two-pronged process. To impeach an official, the House of Representatives must pass articles of impeachment, which formally accuse the President of misbehavior. Once the House votes to impeach, the Senate must hold a trial to decide if the President should be removed from office.

Read more: Here’s How the Impeachment Process Actually Works

Here’s what you need to know about the Presidents who have been impeached — and why they stayed in office.

Andrew Johnson

Lincoln's successor President Andrew Johnson of Tennessee.
PhotoQuest—Getty Images

Why was Johnson impeached?

The aftermath of the Civil War set the stage for the first impeachment of a U.S. President. After President Abraham Lincoln’s death, he was succeeded by his Vice President, Andrew Johnson.

Johnson was a pro-Union Democrat who had refused to secede from the Union along with his state, Tennessee, during the war. However, he was also a racist who favored a lenient approach to Reconstruction, the process of bringing the states of the Confederacy back into the nation. He clashed with Congress throughout his term, vetoing bills he felt were too harsh on the South — including the Freedmen’s Bureau Acts, which gave displaced southerners, including African Americans, access to food, shelter, medical aid and land.

This approach put him at odds with Congress. The final straw came when he replaced Secretary of War Edwin Stanton, a Lincoln appointee who sided with the Radical Republicans, a faction of the party that favored enfranchisement and civil rights for freed African Americans.

Congress produced 11 articles of impeachment, which alleged that Johnson had violated the Tenure of Office Act — a law intended to limit presidential power to remove federal appointees from office — and had found a replacement without consulting the Senate. Johnson was impeached by a two-thirds super majority of the House, and the case moved to the Senate for trial. Years later, the Supreme Court determined that the act was unconstitutional.

Why wasn’t Johnson removed from office?

When he was tried in the Senate, Johnson ultimately held onto his presidency by a single vote, after seven Republicans decided to vote with Senate Democrats to keep him in office.

Johnson’s defense argued that he hadn’t appointed Secretary of War Stanton in the first place, which meant that he wasn’t violating the Tenure of Office Act. They also claimed that Johnson intended to push the Act before the Supreme Court. Historian Hans L. Trefousse argues that the Senators who voted against removal decided that Johnson was being pushed out of office for political reasons: “[The] weakness of the case… convinced many that the charges were largely political, and that the violation of the Tenure of Office Act constituted neither a crime nor a violation of the Constitution but merely a pretext for Johnson’s opponents.”

This result set a major precedent for future presidential impeachments: that Presidents shouldn’t be impeached for political reasons, but only if they commit, as the Constitution stipulates, “treason, bribery or other high crimes and misdemeanors.”

As one of the defecting Republicans, Senator James Grimes, said, “I cannot agree to destroy the harmonious working of the Constitution for the sake of getting rid of an Unacceptable President.”

Bill Clinton

Pres. Bill Clinton emphatically denying having affair with former White House intern Monica Lewinsky.
Diana Walker—Time & Life Pictures/Getty Image

Why was Clinton impeached?

Like Johnson, President Bill Clinton had stirred up a lot of anger in Congress. After his affair with former White House intern Monica Lewinsky became public in January 1998, Clinton at first adamantly denied to federal investigators — and the public — having had “sexual relations” with her.

The articles of impeachment alleged that Clinton had perjured himself by lying to investigators about his relationship with Lewinsky. They also said that he had obstructed justice by encouraging White House staff to deny the affair.

Why wasn’t Clinton removed from office?

The outcome of Clinton’s trial reinforced the precedent that Presidents should only be removed from office only in limited circumstances. While many Senators agreed that Clinton had behaved badly, they ultimately decided that his misconduct wasn’t at the level of “high crimes and misdemeanors.”

Michael Gerhardt, a University of North Carolina professor who specializes in constitutional law, said, “A lot of these people found that there was misconduct, but there wasn’t enough to impeach him.”

Susan Collins, a Republican who ultimately voted against conviction, said in a statement that she didn’t believe that Clinton had committed a crime, but that he had behaved badly. “In voting to acquit the President, I do so with grave misgivings for I do not mean in any way to exonerate this man,” Collins said.

Experts say that the effort to remove Clinton from office was doomed because public opinion turned against removing Clinton from office. In fact, Clinton’s job-approval rating peaked during the week of the impeachment, according to Gallup.

Other Presidents also faced impeachment threats

A demonstration outside the White House in support of the impeachment of President Richard Nixon (1913 - 1994) following the Watergate revelations.
MPI—Getty Images

Given that only two presidents have ever been impeached, more of them have faced Congressional calls for impeachment than one might expect.

The first President the House of Representatives moved to impeach was John Tyler. After succeeding President William Henry Harrison, who died after just one month in office, Tyler vetoed legislation backed by his own Whig Party and that Harrison had promised to support. The Whigs kicked Tyler out of their party, and the House received a petition for a resolution asking him to resign or else face the possibility of impeachment. Yet Congress ultimately didn’t pursue an impeachment.

The president best known for coming to the brink of impeachment — but not actually getting impeached — was Richard Nixon. During the Watergate scandal, the House Judiciary Committee filed three articles of impeachment against the president for “high crimes and misdemeanors.” However, Nixon resigned his office on Aug. 9, 1974, before the impeachment could move forward.

In recent American history, Presidents from Herbert Hoover to Barack Obama have faced discussion, ranging from credible to dubious and politically charged, of their impeachment. And even at moments of great popularity, all Presidents will know, in the back of their minds, that impeachments are, however rare, a possibility — which is just what the Constitution’s framers intended.

“A good magistrate will not fear them,” said Elbridge Gerry of impeachments, at the Constitutional Convention. “A bad one ought to be kept in fear of them.”

Write to Tara Law at tara.law@time.com.

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