. >> abby phillip is a cnn political correspondent, john dean is a cnn contributor and the white house council for president nixon and jeffrey tullis is a professor. also, the co author of legacies of losing in american politics. jeffrey, let me start with leader is in your words, in literal violation of the oath. he will have to take at the start of the senate trial, can you tell me why? >>. >> there's a new one all senators have to take, including co constitution requires, that's different from the oath they take as senators. the senate operating trial is a different institution, it recomposes itself into an institution in which the senators are no longer the senators as they used to be, but are in combination of judge and jurors, the other important thing about this, they're all equal, he's no longer majority leader, there's no president protem and so forth. we're in a situation in which they'll have to change their character. when it does, it's a different institution, and in the previous two, and we've only had two instances in which impeachment has gone to the senate for a trial,