"Conditions may, and are not unlikely to arise, some day, when the exercise of the power to impeach and remove the President may be quite as essential to the preservation of our political system as it threatened to become in this instance destructive of that system. Should that day ever come, it is to be hoped that the remedy of impeachment, as established by the Constitution, may be as patriotically, as fearlessly, and as unselfishly applied as it was on this occasion rejected."