Meanwhile his Democratic counterpart emphasised that impeachment has been reserved for offences that undermine the capacity of a judge or a president to carry out the duties of his office, rather than for private crimes.

ECONOMIST: The impeachment hearings

But you cannot ignore the circumstances in which the conduct occurs or abandon the core principle that impeachment should be reserved for those cases in which the president's very capacity to govern is called into question.

CNN: Transcript: White House Counsel Ruff's opening statement