Grand Inquests: The Historic Impeachments of Justice Samuel Chase and President Andrew Johnson by William Rehnquist. This is an interview with the late Chief Justice of the US Supreme Court. In it, William Rehnquist discusses his book Grand Inquests: The Historic Impeachments of Justice Samuel Chase and President Andrew Johnson.
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LAMB: In both the Samuel Chase situation and the Andrew Johnson situation, they were impeached by the House, but not convicted by the Senate. How come? I know that's a simple question, but it's a long answer.
REHNQUIST: It is a fairly long answer, and it isn't the easiest question in the world to answer. It's much easier to answer the question about Andrew Johnson than it is about Samuel Chase because some 30 of the senators out of the 54 who were in the Senate at the time of the Andrew Johnson impeachment after the Civil War left statements of their views. As to the Chase impeachment that took place in 1805, no one left any statement there. We have the letter of one of the senators to his wife who stayed at home in New York while he came down to Washington, giving a couple sentences as to why he voted the way he did. But in each case, the same thing happened. The majority party that controlled the Congress controlled both houses, and the House of Representatives voted to impeach with the pretty solid support of the majority party. The Senate was also controlled by that same party, to such an extent that if all the senators of that party -- the Jeffersonian Republicans in 1805 in the Senate, the Republicans or the present-day Republican ancestors in 1868 -- had voted to convict, each of those defendants would have been convicted. But in each case, a number of them broke ranks. Enough of them broke ranks so that there was an acquittal rather than a conviction, which showed that party discipline was not going to be the controlling factor in the use of impeachment.