Under Article II, Sec. 4 of the US Constitution, Congress has the power to impeach the President, the Vice President and "all civil Officers of the United States" for "Treason, Bribery, or other high Crimes and Misdemeanors." If the House approves one or more articles of impeachment by a simple majority vote, the Senate conducts a trial that will result in a removal from office only if two-thirds of the Senate votes to convict.

This publication examines (I) the process of impeachment, (II) the two prior instances in which a US President has been impeached, but not convicted (as well as the instances in which judges have been impeached) and (III) the impeachment efforts targeting US President Donald Trump.

The Process of Impeachment

The impeachment process formally begins in the House of Representatives, with the filing of articles of impeachment, and is followed by a trial in the Senate. Impeachment proceedings can be triggered by lawmakers or prompted by individuals outside the US Congress, such as through recommendations from entities like the Judicial Conference of the United States, independent counsels with substantial and credible information that could constitute grounds for impeachment, or a charge from a state or territorial legislature or grand jury. But, whatever the source, the process cannot begin until one or more Members of Congress formally introduces a resolution setting forth the basis for impeachment.

Although the Constitution speaks in terms of "Treason, Bribery, or other high Crimes and Misdemeanors," non-criminal activity has also served as grounds for impeachment. Grounds for impeachment fall into three broad categories: (1) conduct unsuited to the function or purpose of the office, (2) abuse of office for personal gain or an improper purpose and (3) improperly exceeding or abusing the powers of the office.

Historically, the first category includes actions such as providing false information on federal income tax forms, appearing on the bench intoxicated, alleged sexual assault and judicial favoritism. President Clinton's 1998 impeachment articles most closely fall into this category, as lying to a grand jury and obstructing justice are considered unsuited to the presidency. The second category, abusing the office for personal gain or improper purpose, has involved false contempt charges, receiving payments and favors in exchange for judicial outcomes and influencing cases.

Two federal judges have been removed under the third category for abuse of power. President Andrew Johnson's impeachment, involving the removal of a cabinet member, can also be seen as exceeding his presidential powers. These categories are not definitive or exhaustive, but exist to summarize the majority of impeachment proceedings conducted thus far in the US.

Each individual charge of alleged wrongdoing is an article; together, the charges are the articles of impeachment. The articles are generally referred to the House Judiciary Committee, which conducts an initial investigation and then votes on a resolution of one or more articles. Next, the entire House considers the resolution. Members can adopt the resolution as a whole or vote on each article individually. If a simple majority of the House votes in favor of one or more of the articles, then the individual is considered impeached by the House.

After the House votes to impeach, "managers," who will act as the prosecution during the Senate trial, are selected from among House members. Once the proceedings move to the Senate, the individual will enter a pleading and a "trial date" is set. There are no formal rules governing how the trial will be conducted. In practice, the Senate Majority Leader and the Senate Minority Leader negotiate terms broadly acceptable to their respective caucuses, which then are voted upon.1 During the trial, witnesses can be subpoenaed, evidence considered and testimony taken, either by the full Senate or a committee of Senators selected by the Presiding Officer. The Presiding Officer is traditionally the Vice President, acting in his role as the President of the US Senate. Notably, however, the Chief Justice of the Supreme Court presided over the two instances where a sitting US president was impeached, as discussed in Section II.

At the close of the trial, the Senate deliberates and votes on each individual article. A two-thirds vote of Senators present is required for conviction. Because each article contains a separate charge, an individual may be convicted of all, some or none of the articles. Conviction on a single article will result in removal from office. The Senate may then vote to disqualify the individual from ever serving in an "office of public trust" in the US again. This vote requires only a simple majority to pass.

Notably, the Constitution specifies that an individual is not immune from criminal liability once convicted. An individual who is facing impeachment, or who has already been impeached, may face separate criminal proceedings.

Historical US Impeachments

Nineteen individuals have been impeached by the House, but three individuals resigned after the House took action, resulting in only 16 full impeachment trials in the Senate. These 16 trials resulted in eight convictions, all of them federal judges.

Only two presidents have been impeached: Andrew Johnson and Bill Clinton. They are discussed, in turn, below.2

Andrew Johnson

In 1868, the House of Representatives adopted 11 articles of impeachment against Andrew Johnson. Many of them dealt with President Johnson's violation of the Tenure of Office Act – he replaced his Secretary of War in violation of the Act. The Senate only voted on three of the articles, each of which fell one vote short of the two-thirds majority required for conviction. After the three votes failed, the trial adjourned without votes on the remaining articles. That year, President Johnson failed to receive the Democratic nomination for president necessary for reelection and left office at the end of his term in 1869.

Bill Clinton

In 1998, House lawmakers considered four articles of impeachment against Bill Clinton. During a sworn deposition for a sexual harassment lawsuit stemming from his time as Governor of Arkansas, President Clinton denied a sexual relationship with White House intern Monica Lewinsky. This relationship later proved to be true and President Clinton was impeached on two articles: lying to a grand jury and obstruction of justice. President Clinton was ultimately found not guilty under both articles.


1. For more information on the politics of this process during President Bill Clinton's impeachment trial, see https://www.washingtonpost.com/opinions/2019/10/23/ tom-daschle-trent-lott-senate-can-hold-fair-impeachment-trial-we-did-it/

2. Impeachment proceedings began against a third, Richard Nixon, and reached the House Judiciary Committee stage before President Nixon resigned. As impeachment is meant to remediate bad players within the government, and has no bearing on criminal liability, impeachment proceedings against President Nixon stopped once he resigned. He was spared any criminal prosecution by President Gerald Ford, who issued a full and unconditional pardon of President Nixon's activities while president.

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