Only three U.S. presidents have been formally impeached by Congress—Andrew Johnson, Bill Clinton and Donald Trump. One of those presidents, Donald Trump, was impeached twice during his single term. No U.S. president has ever been removed from office through impeachment.

In addition to Johnson, Clinton and Trump, only one other U.S. president has faced formal impeachment inquiries in the House of Representatives: Richard Nixon. Many other presidents have been threatened with impeachment by political foes without gaining any real traction in Congress.

The framers of the Constitution intentionally made it difficult for Congress to remove a sitting president. The impeachment process starts in the House of Representatives with a formal impeachment inquiry. If the House Judiciary Committee finds sufficient grounds, its members write and pass articles of impeachment, which then go to the full House for a vote.

A simple majority in the House is all that’s needed to formally impeach a president. But that doesn’t mean he or she is out of a job. The final stage is the Senate impeachment trial. Only if two-thirds of the Senate find the president guilty of the crimes laid out in the articles of impeachment is the POTUS removed from office.

Although Congress has impeached and removed eight federal officials—all federal judges—no president has ever been found guilty during a Senate impeachment trial. Andrew Johnson came awfully close, though; he barely escaped a guilty verdict by one vote.

If a president is acquitted by the Senate, the impeachment trial is over. But if he or she is found guilty, the Senate trial moves to the sentencing or “punishment” phase. The Constitution allows for two types of punishments for a president found guilty of an impeachable offense: “Judgment in Cases of 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.”

The first punishment, removal from office, is automatically enforced following a two-thirds guilty vote. But the second punishment, disqualification from holding any future government position, requires a separate Senate vote. In this case, only a simple majority is required to ban the impeached president from any future government office for life. That second vote has never been held since no president has been found guilty in the Senate trial.

Johnson was elected as Abraham Lincoln’s vice president in 1864. The toughest decision facing Lincoln’s second term was how to reestablish ties with the Confederate states now that the Civil War was over. Lincoln’s plan for Reconstruction favored leniency while so-called “Radical Republicans” in his party wanted to punish Southern politicians and extend full civil rights to freed slaves.

Lincoln was assassinated only 42 days into his second term, leaving Johnson in charge of Reconstruction. He immediately clashed with the Radical Republicans in Congress, calling for pardons for Confederate leaders and vetoing political rights for freedmen. In 1867, Congress retaliated by passing the Tenure of Office Act, which barred the president from replacing members of his cabinet without Senate approval.

Believing the law to be unconstitutional, Johnson went ahead and fired his Secretary of War, an ally of the Radical Republicans in Congress. Johnson’s political enemies responded by drafting and passing 11 articles of impeachment in the House.

"Sir, the bloody and untilled fields of the ten unreconstructed States, the unsheeted ghosts of the two thousand murdered negroes in Texas, cry [...] for the punishment of Andrew Johnson," wrote the abolitionist Republican Representative William D. Kelley from Pennsylvania.

Johnson was impeached in the House of Representatives by 126 votes to 47, but narrowly avoided a two-thirds guilty verdict in the Senate by a single vote. After his acquittal, he served out the rest of his term and became the first (and only) former U.S. president to be elected to the Senate.

Clinton was plagued by legal troubles and scandals from the moment he entered the White House. In 1993, Clinton and his First Lady, Hillary, were the subject of a Justice Department investigation into the so-called Whitewater controversy, a botched business deal from their days in Arkansas. And in 1994, Clinton was sued for sexual harassment by Paula Jones, who claimed Clinton exposed himself to her in a hotel room in 1991.

Interestingly, it was a combination of both legal cases that would ultimately lead to Clinton’s impeachment. Independent counsel Kenneth Starr was appointed by the Justice Department to investigate the Whitewater affair, but he couldn’t find any impeachable evidence. Meanwhile, lawyers for Jones got a tip that Clinton had an affair with a 21-year-old White House intern named Monica Lewinsky, a claim that both Lewinsky and Clinton denied under oath.

Starr switched the focus of his investigation when he received 20 hours of taped phone conversations between Lewinsky and Linda Tripp, a former White House colleague, in which Lewinsky alludes to the affair. Starr then got the FBI to fit Tripp with a wire to meet with Lewinsky at a Ritz-Carlton hotel outside Washington, DC, when Lewinsky again admitted to a sexual relationship with the president.

When the story went public, Clinton was forced to address the accusations on national television.

“I want you to listen to me,” Clinton famously said. “I did not have sexual relations with that woman, Miss Lewinsky. I never told anybody to lie, not a single time, never.”

Starr’s investigative team ended up producing a long and lurid report detailing Clinton’s sexual dalliances with Lewinsky and providing evidence that Clinton lied under oath (perjury) in an effort to obstruct the Starr investigation.

On December 19, 1998, the House of Representatives voted to impeach Clinton on two separate counts: perjury and obstruction of justice. But in the ensuing five-week Senate trial, Clinton was acquitted on both counts.

Despite a very public and embarrassing scandal, and being only the second president in history to be impeached, Clinton’s job approval rating peaked at 73 percent in 1999.

On September 24, 2019, House Speaker Nancy Pelosi announced a formal impeachment inquiry into President Trump regarding his alleged efforts to pressure the President of Ukraine to investigate possible wrongdoings by his political rival, former Vice President Joe Biden.

The decision to authorize the impeachment inquiry came after a leaked whistleblower complaint detailed a July phone conversation between Trump and President Volodymyr Zelensky in which Trump allegedly tied Ukrainian military aid to personal political favors. The White House later released a reconstructed transcript of the phone call, which many Democrats argued demonstrated that Trump had violated the Constitution.

On December 18, 2019, President Trump became the third U.S. president in history to be impeached as the House of Representatives voted nearly along party lines to impeach him over abuse of power and obstruction of Congress. No Republicans voted in favor of either article of impeachment, while three Democrats voted against one or both. On February 5, 2020, the Senate voted largely along party lines to acquit Trump on both charges.

On January 11, 2021, House Democrats introduced a second article of impeachment that accused the president of “incitement of insurrection.” The article cited phone calls, speeches and tweets by President Trump that allegedly incited a violent crowd that attacked the U.S. Capitol on January 6, 2021.

The House of Representatives voted to impeach President Trump again on January 13, 2021, making him the only president in history to be impeached twice. Unlike Trump’s first impeachment, 10 Republicans joined House Democrats who unanimously voted in favor of impeachment. One hundred and ninety-seven Republicans voted against the second impeachment. The Senate trial took place after President Trump left office. He was found not guilty, though seven Republican senators joined Democrats in voting to convict, making it the most bipartisan Senate impeachment vote in history.

Despite being complicit in one of the greatest political scandals in U.S. presidential history, Richard Nixon was never impeached. He resigned before the House of Representatives had a chance to impeach him. If he hadn’t quit, Nixon would likely have been the first president ever impeached and removed from office, given the crimes he committed to cover up his involvement in the Watergate break-ins.

On July 27, 1974, after seven months of deliberations, the House Judiciary Committee approved the first of five proposed articles of impeachment against Nixon, charging the president with obstruction of justice in an effort to shield himself from the ongoing Watergate investigation. Only a handful of Republicans in the judiciary committee voted to approve the articles of impeachment, and it was unclear at the time if there would be enough votes in the full House to formally impeach the president.

But everything changed on August 5, 1974, when the Supreme Court ordered Nixon to release unedited tapes of his Oval Office conversations with White House staffers during the Watergate investigation. The so-called “smoking gun” tapes included Nixon proposing the use of the CIA to obstruct the FBI investigation, and paying hush money to the convicted Watergate burglars. The transcript included the following:

NIXON: How much money do you need?

JOHN W. DEAN: I would say these people are going to cost, uh, a million dollars over the next, uh, two years. (Pause)

NIXON: We could get that.

Once the tapes were made public, Nixon got word from Republican congressional leadership that all but 15 Senators would likely vote against him in an impeachment trial, more than enough to remove him from office. To save himself the indignity of becoming the first sitting president fired by Congress, Nixon resigned on August 8, 1974.

Nixon was pardoned of criminal charges by Gerald Ford, but many of his Watergate conspirators weren’t so lucky. Most of his White House legal counsel, including John Dean, went to jail for their involvement in Watergate.

A significant number of U.S. presidents have faced calls for impeachment, including five of the past six Republican presidents. But few of those accusations were taken seriously by Congress.

There were even rumblings about impeaching the nation's first president, George Washington, by those who opposed his policies. Those calls, however, did not reach the point of becoming formal resolutions or charges.

John Tyler was the first president to face impeachment charges. Nicknamed “His Accidency” for assuming the presidency after William Henry Harrison died after just 30 days in office, Tyler was wildly unpopular with his own Whig party. A House representative from Virginia submitted a petition for Tyler’s impeachment, but it was never taken up by the House for a vote.

Between 1932 and 1933, a congressman introduced two impeachment resolutions against Herbert Hoover. Both were eventually tabled by large margins.

More recently, both Ronald Reagan and George H.W. Bush were the subject of impeachment resolutions submitted by Henry B. Gonzales, a Democratic representative from Texas, but none of the resolutions were taken up for a vote in the House Judiciary Committee.

George W. Bush faced a slightly more serious impeachment threat when Democratic Representative Dennis Kucinich introduced a House resolution charging Bush with a litany of high crimes and misdemeanors, including war crimes. The House voted 251 to 166 to refer the resolution to the House Judiciary Committee, but House Speaker Pelosi said any talk of impeachment was “off the table.”

Barack Obama was also accused of “high crimes and misdemeanors” befitting impeachment. In 2012, Republican Representative Walter Jones submitted a House resolution charging the president with authorizing military action in Libya without the consent of Congress. The resolution was referred to the Judiciary Committee where it was never brought up for a vote.