Trump is facing impeachment over whistleblower's allegations that he threatened to withhold $400 million in aid to Ukraine to secure a promise from the country's President Volodymyr Zelenskiy to investigate political rival Joe Biden, and his son Hunter, who sat on the board of a Ukrainian energy company.
Trump has denied wrongdoing and assailed the probe.
Here is a look at how the process works.
What is impeachment?
The founders of the United States created the Office of the Presidency and feared its powers could be abused. So they included in the US Constitution a procedure for removing a sitting President from office.
Under the Constitution, the President can be removed from office for "treason, bribery, or other high crimes and misdemeanours."
What does it mean?
What exactly that means is unclear. Historically, it can encompass corruption and other abuses of the public’s trust.
A President does not need to have violated a specific criminal law to have committed an impeachable offense.
Many legal commentators have said that pressuring a foreign leader to interfere in a US election is the sort of conduct the nation’s founders would have considered an impeachable offense.
How does it work?
A misconception about “impeachment” is that it refers to the removal of a President from office. In fact, impeachment refers only to the House, the lower chamber of Congress, bringing charges - similar to an indictment in a criminal case.
'Articles of impeachment'
If a simple majority of the House’s 435 members approves bringing charges, known as "articles of impeachment," the process moves to the Senate, the upper chamber, which holds a trial to determine the president’s guilt.
In such a trial, House members act as the prosecutors, the senators as jurors; the chief justice of the US Supreme Court presides. A two-thirds majority vote is required in the 100-member Senate to convict and remove a president.
Lawmakers are not required to prove their case beyond a reasonable doubt — the evidentiary standard in a criminal case.
Party breakdown in Congress?
The House has 235 Democrats, 199 Republicans, and one independent. As a result, the Democrats could impeach Trump with no Republican support.
In 1998, when Republicans had a House majority, the chamber voted largely along party lines to impeach President Bill Clinton, a Democrat. Two and a half months passed between the House voting to move forward with impeachment proceedings against Clinton and his impeachment.
The Senate now has 53 Republicans, 45 Democrats and two independents who usually vote with the Democrats. Conviction and removal of a president would require 67 votes. So, for Trump to be removed from office via impeachment, at least 20 Republicans and all the Democrats and independents would have to vote against him.
The Republican majority in the Senate could vote to immediately dismiss the charges against Trump without considering evidence.
Has any President been impeached?
No president has ever been removed from office as a direct result of impeachment. President Richard Nixon resigned in 1974 before he could be impeached while Andrew Johnson in 1868 and Bill Clinton were impeached by the House but not convicted by the Senate.
Who becomes President if Trummp is removed?
In the unlikely event of Senate convicting Trump, Vice President Mike Pence would become president for the remainder of Trump’s term, which ends on January 20, 2021.
Is there another way to remove a President?
Under 25th Amendment, a President can be replaced by Vice President if the chief executive was unable to do his job, such as due to a disabling medical or mental condition. That process begins with the vice president and a majority of the members of the Cabinet notifying Congress that the president is not capable of performing his job.