Tenure of Office Act) 禁止总统在没有得到参议院同意之下，开除任何政府官员，总统自己的内阁成员也包括在内。詹森认为这项法案违反宪法规定，所以是无效的。他开除了长久以来的政治对手：战争部部长爱德温．史坦顿 (Edwin
M. Stanton) ，而挑战了众议院通过的法案。
美国众议院接着决定根据宪法规定之严重罪刑与不当行为，弹劾詹森。詹森被指控破坏法律以及其他的罪行。但是在参议院的审判里 (根据宪法，这里是举办弹劾听证会的场所) ，这些指控都太为薄弱，所以有七位共和党籍的参议员拒绝判决这位民主党籍的总统有罪。于是，最后的投票结果因为一票之差，而无法达到三分之二的定罪规定。
That same day, Congress passed a law that limited the power of the president. The Tenure of Office Act prohibited the president from removing any government official, including his own cabinet members, without the Senate's approval. Johnson maintained the law was unconstitutional and thus invalid. He fired Secretary of War Edwin M. Stanton, a political enemy, in open defiance of the law.
The House of Representatives then decided to impeach the president, charging him with "high crimes and misdemeanors" as required by the Constitution. Johnson was charged with breaking the law, among other things. During his trial before the Senate (where impeachment hearings are held, according to the Constitution), the charges were shown to be so weak that seven Republicans refused to convict the Democratic president. The votes thus fell one short of the two-thirds necessary for conviction.
Johnson did not attend his trial. When he heard the results, the president broke into tears.