Tuesday, January 5, 1999 Published at 18:06 GMT
Impeaching President Johnson
Trial against Andrew Johnson in the Senate (Senate Historical Society drawing)
Before President Clinton, only one other US president had ever been impeached.
Johnson, a democrat, went on trial in the Senate, just as President Clinton expects to. He narrowly escaped removal from office - and had to fight hard to do so.
Johnson had become president following Abraham Lincoln's assassination in April 1865, just days after the Civil War ended. As a Southerner and a war Democrat, he had been chosen as President Lincoln's running mate to balance the Union ticket in the year before.
Saved by a single vote
Like President Clinton, Mr Johnson was a Democratic president who had to contend with a Republican-controlled Congress. In particular, Mr Johnson and the radical Republican majority clashed over the President's desire to scale back his predecessor's Reconstruction legislation.
Calls for President Johnson's impeachment were based on charges that he had violated the Tenure of Office Act which prohibited a president from dismissing any officer confirmed by the Senate without first getting its approval.
The first attempt to impeach President Johnson failed, but a couple of months later the House of Representatives passed a resolution of impeachment - even before it adopted 11 articles detailing the reasons why.
The Senate was organised as a court to hear the charges in March 1868. The president himself did not appear.
In spite of great pressure brought to bear on several Senators, the Senate did not convict the president.
The vote taken on 16 May on the 11th article of impeachment, a catchall of several charges, was 35-19 - one vote short of the two thirds majority needed. Enough Republicans broke ranks to make the difference.
The result was the same when votes were taken later on the second and third articles. The chamber adjourned without voting on the remaining charges.
President Johnson served the remainder of Lincoln's term but failed to win his party's nomination for president.
In 1874 he was elected from Tennessee to the very Senate that had tried to convict him, but he died a few months after taking his seat.
Partisan tribunal or judicial inquiry?
At issue in a Senate trial such as that which Johnson underwent - and which now faces President Clinton - is whether it will become "a partisan tribunal, which would be willing to undermine the fundamental principles of the Constitution in order to remove a political enemy from office, " writes current US Chief of Justice William Rehnquist in his 1992 book.
Mr Rehnquist, set to preside at President Clinton's trial, says President Johnson's acquittal was a victory for the independence of the executive branch and an important precedent.
Had the Senators convicted him, the verdict would have meant officials can be impeached just because Congress disagrees with their political views.
Members of the Senate now face the same test as their predecessors 130 years ago.