President Donald Trump became the fourth president to ever face a formal impeachment inquiry after Speaker Nancy Pelosi endorsed the move.
Andrew Johnson, Richard Nixon and Bill Clinton were the others to meet that fate. Johnson and Clinton were both impeached by the House, while Nixon resigned before a vote could take place. To date, no president has been removed from office by impeachment.
Impeachment is a long, complicated process. Here’s a guide to the steps going forward and a look at what happened in the past.
The political climate has to be right for Congress to act.
Past impeachment inquiries have been fueled by scandals, especially episodes that sink support for the president in Congress and with the broader public.
How it's playing out now
A whistleblower’s complaint that Trump pressured the Ukrainian president to investigate Joe Biden, a potential 2020 rival, was the final straw for House Democrats already pondering impeachment.
In history
Clinton’s impeachment process began when he was accused of lying under oath about his sexual relationship with Monica Lewinsky.
After the break-in of the Democratic National Committee headquarters in 1972, Nixon outraged the country when he tried to cover up his involvement with the crime.
The push to impeach Johnson came after he fired his Secretary of War, Edwin Stanton. Congress was outraged because it was a direct violation of the newly passed Office of Tenure Act, which prohibited removal of certain Cabinet officials without the Senate’s consent.
Impeachment always starts in the House.
The sitting speaker of the House must give her approval for impeachment proceedings.
How it's playing out now
House Democrats were already investigating Trump for obstruction of justice and other potential crimes when the Ukraine scandal erupted. Speaker Nancy Pelosi had long resisted impeachment, but soon she and her caucus felt they had no choice but to pursue an impeachment inquiry. “That’s what I’ve said all along," she told POLITICO. "When we get the facts, we will be ready. And we’re ready.”
In history
After four years of investigations into several Clinton scandals, the House began impeachment proceedings for Clinton in October 1998.
As the Watergate scandal snowballed, the House began impeachment proceedings for Nixon in October 1973.
After repeated clashes between congressional Republicans and Johnson over Reconstruction policies, Congress passed a resolution to begin impeachment proceedings in February 1868.
House committees investigate and write articles of impeachment.
If the Judiciary Committee approves any articles of impeachment, the full House will vote on the charges against the president.
How it's playing out now
House Democrats are zeroing in on Trump’s alleged Ukraine misconduct and any related obstruction of Congress in that investigation. But they could also consider accusing him of other alleged high crimes and misdemeanors related to obstructing Robert Mueller’s Russia probe, silencing women who have had sexual encounters with him, or profiting off his presidency.
In history
The House Judiciary Committee wrote four articles of impeachment for Clinton: a pair of perjury charges, including lying about his relationship to Monica Lewinsky, obstructing justice by attempting to tamper with witnesses of the sexual harassment case brought against him, and an article accusing Clinton of abuse of power.
During Nixon’s impeachment process, three out of five articles of impeachment were passed by the Judiciary Committee: Obstruction of justice by covering up the illegal entry of the DNC, abuse of power and contempt of Congress by refusing to give up secret tapes of conversations between him and his aides. Two articles did not pass, including allegations around a secret bombing of Cambodia and Nixon’s failure to pay taxes.
Eleven articles of impeachment were drafted for Johnson. Eight focused on his violation of the Office of Tenure Act. Critics called some articles “petty”, including the article claiming Johnson orated “with a loud voice, certain intemperate, inflammatory, and scandalous harangues.”
A majority vote in the House is needed to impeach.
At least 218 out of 435 representatives are needed to approve any of the articles of impeachment presented by the Judiciary Committee.
How it's playing out now
We haven’t reached this point yet, but if all representatives vote along party lines, there are more than enough Democrats (235) to impeach Trump.
In history
The House passed two articles of impeachment against Clinton and rejected two others. The first to be approved was lying to a grand jury, which passed 228-206; a charge of obstruction of justice was passed on a 221-212 vote. A second count of perjury was defeated, 205-229, and an article accusing Clinton of abuse of power was rejected, 148–285.
The Judiciary Committee approved articles of impeachment, but Nixon resigned before a vote reached the floor; impeachment was essentially a certainty.
All 11 articles of impeachment against Johnson were passed.
If the House impeaches the president, the Senate holds a trial.
At the outset, the Senate passes a resolution setting trial procedures and how to handle witness testimony and evidence. Typically, members of the House Judiciary Committee manage the argument for impeachment and the president has his own defense lawyers on the floor.
How it's playing out now
Despite some speculation to the contrary, Majority Leader Mitch McConnell has said that the Senate would have to act in some form if the House impeaches Trump. But it’s not clear whether the Senate would vote to simply dismiss the charges or hold a full trial.
In history
Senate Majority Leader Trent Lott and Senate Minority Leader Tom Daschle crafted a bipartisan agreement on how to run Clinton’s trial, which took place in January 1999.
Nixon resigned before the Senate had a chance to weigh in.
In March 1868, the Senate began the country’s first presidential impeachment trial, which was mostly open to public spectators.
After the trial, the Senate votes.
A two-thirds majority, or 67 of 100 senators, is needed for the president to be convicted and removed from office.
How it's playing out now
For Trump to be convicted, at least 20 Republican senators would have to join all Democrats. At the moment, that seems unlikely but more developments could shake GOP support for Trump.
In history
Clinton was acquitted on both articles of impeachment with some bipartisan support. The Senate voted to acquit him on charges of lying to a grand jury on a 45-55 vote and on charges of obstruction of justice on a 50-50 vote.
Nixon resigned before the Senate had a chance to weigh in.
The Senate, which at the time included 54 members representing 27 states, voted 35-19 in favor of removing Johnson from office. The Senate tally was one vote short of the two-thirds threshold and Johnson remained in office.