William Rehnquist, Chief Justice of the Supreme Court

Chief Justice William Rehnquist

A dyed-in-the-wool Republican, Justice Rehnquist, 74, presided at the Senate trial.

The Harvard-educated Lutheran was appointed to the Supreme Court by President Nixon in 1972 and promoted to Chief Justice by President Reagan in 1986.

Lawyer Alan Dershowitz: Chief Justice will play key role early on

Justice Rehnquist is well-known in court for his brisk manner.He does not suffer fools, cuts lawyers off and he corrects mispronunciations and misuse of words.

He has also written a book about the 1868 trial of Andrew Johnson - the only other American president to face an impeachment trial. In the book, Grand Inquests, he warns that impeachment must only be used for serious abuses of office and he applauds Johnson's acquittal.

Profile: William Rehnquist

Sen Robert Byrd, Democrat

Sen Robert Byrd

Democratic Sen Robert C Byrd of West Virginia is considered the Senate's leading expert on rules and procedures. He studies Senate rules in his spare time on the weekends, and he wrote the book The Senate 1789-1989.

His commitment to the Constitution put him at odds with his own party. He opposed Mr Clinton's efforts to win line-item veto power for the president on the basis that it violated the separation of powers laid out in the Constitution.

For his non-partisan commitment to the Constitution and procedure, Republicans looked to this senior statesman of the Democratic Party for guidance on how to proceed with impeachment. He called for a bipartisan solution and left open the possibility of censure either before or after a trial had begun.

Sen Tom Daschle, Democrat

Sen Tom Daschle

As Senate Minority Leader, Tom Daschle took the lead in representing Democrats in trial preparations and negotiations. Well-liked by his Senate colleagues and a good friend to the White House, the liberal South Dakotan argued first for censure then for a no-witness trial.

But Sen Daschle was not partisan. Like his Republican counterpart, Sen Trent Lott, he worked hard behind the scenes not to let rancour degrade the institution of the Senate.

Sen Orrin Hatch, Republican, Chair Senate Judiciary Committee

Sen Orrin Hatch

Senator Orrin Hatch was one of the first Republicans to suggest a way out for President Clinton. He said during the summer that Mr Clinton should apologise and seek the forgiveness of Congress and the American people.

The mild mannered Mr Hatch, a Mormon representing the State of Utah, was angered by the President's half-hearted admissions and was overheard calling him, in uncharacteristically harsh language, a "jerk."

The conservative Senator is Chairman of the Senate Judiciary Committee.

Orrin Hatch, 64, is a songwriter, whose belief in God and Country are his main subjects. He has recorded several CD's with singer Janice Kapp Perry. One title is "Heal Our Land". Will he be able to do this in the Senate?

Sen Joseph Lieberman, Democrat

Sen Joseph Lieberman

Joe Lieberman, the Democratic Senator from Connecticut, has been a personal and political friend to Bill Clinton for nearly 30 years. But that friendship was severely tested in September, when Mr Lieberman took to the Senate floor to condemn the president for his "immoral" and "disgraceful" behaviour in the Monica Lewinsky affair.

The Senate's only practising Orthodox Jew, Lieberman is widely respected by both parties for his thoughtful and deeply-held views on moral issues.

Sen Trent Lott, Republican, Senate Majority Leader

Senate Majority Leader Trent Lott

With the demise of Newt Gingrich, Trent Mr Lott is the de facto national leader of the Republican Party. He succeeded Bob Dole as Senate majority leader in 1996 and has been a crucial player in the negotiations surrounding the trial of the President.

It is tempting to see Mr Lott as an uncompromising hard-liner - much of his rhetoric is indeed designed to appeal to the Republicans' hard-core right wing activists - but he has also revealed a pragmatic streak in dealings with the Clinton White House.

He made it plain that he felt a trial of the president was inevitable and that no back-room deals should circumvent it. By casting suspicions on the timing of Bill Clinton's air strikes on Iraq, he infuriated the White House and shocked some of his own colleagues, though he later backtracked somewhat from his original outspoken criticisms.

Sen Mitch McConnell, Republican

Sen Mitch McConnell

A member of the "Conservative Coalition," a bi-partisan group of Senators representing southern states, Kentucky Sen Mitch McConnell was Chairman of the Senate Ethics Committee during the sexual misconduct investigation of fellow Republican Senator Bob Packwood.

Sen McConnell is Chairman of the Senate Rules Committee.

Sen Arlen Specter, Republican

Sen Arlen Specter

An iconoclastic ex-prosecutor - all that is certain about Senator Arlen Specter's role in deciding President Clinton's fate was that he would confound his critics and supporters alike.

The four-term Republican senator from Pennsylvania is a moderate on social issues, which has opened him up to attacks from the right-wing of his own party, but he takes often hard-line, letter-of-the-law positions which infuriate his Democrat opponents.

He is remembered for his withering cross-examination of Anita Hill. She accused Clarence Thomas of sexual harassment during the hearings on his appointment to the Supreme Court.