But history provides no reliable guide about the consequences facing Trump ahead, as impeachment is a lengthy, complicated process spelled out in the Constitution.
Americans often equate impeachment with the removal of a president or other federal officials from office for committing a crime. But that’s incorrect. Though two presidents have previously been impeached, Congress has never successfully removed a sitting president.
Here are the times American presidents have faced impeachment, or come close.
When President Abraham Lincoln was assassinated, Andrew Johnson became the 17th president of the United States and served from 1865 to 1869.
Johnson was impeached by the House of Representatives in 1868 after a political conflict with Congress involving his Reconstruction policies after the Civil War and his removal of Secretary of War Edwin Stanton.
Thirty-five senators voted to find him guilty of the charges – a single vote short of the two-thirds majority required for conviction and removal from office.
More than a century later, President Bill Clinton, who served from 1993 to 2001, was impeached for perjury and obstruction of justice in the wake of his extramarital affair with White House intern Monica Lewinsky.
Similar to Johnson, the Senate failed to muster the two-thirds majority for a conviction on either of the charges, and Clinton went on to serve the remainder of his second term in office.
The one who almost was: Richard Nixon
In 1974, President Richard Nixon was on the verge of impeachment over his role in the Watergate scandal.
The House Judiciary Committee approved three articles of impeachment against him alleging obstruction of justice, abuse of power and contempt of Congress. But Nixon resigned from office before the charges were taken up by the full House.
He addressed the nation in a speech from the Oval Office after it became apparent with near-certainty that he would be impeached.
"I have never been a quitter. To leave office before my term is completed is abhorrent to every instinct in my body," Nixon said. "But as president, I must put the interest of America first. America needs a full-time president and a full-time Congress, particularly at this time with problems we face at home and abroad."
What will become of Trump?
It's unclear how the inquiry will play out.
If the House were to initiate impeachment proceedings, it’s possible they would have the votes to approve impeachment articles against Trump.
Democrats hold a 235-198 majority in the House, giving them far more than the 218 votes needed to impeach.
However, in the Senate, Republicans hold a 53-47 advantage over Democrats, and to remove the president from office, Democrats would have to persuade some 20 Republicans to vote for his conviction.
A two-thirds majority, or 67 senators, is needed to convict and remove the accused from office.
This article originally appeared on USA TODAY: Trump impeachment inquiry: Has the U.S. impeached a president?