High crimes and misdemeanors is a phrase that is at once flexible (because it requires case-by-case consideration), and also it offers 400 years of guidance in the form of prior practice with the term on which one could rely in identifying the kinds and degrees of misbehavior that ought to be impeachable.
High crimes and misdemeanors is conduct which the Constitution established — beyond serious dispute — to extend far beyond mere criminal conduct. Why? Because any standard permitting the removal of presidents only for indictable crimes would leave the nation defenseless against the most dangerous kinds of presidential behavior.
High crimes and misdemeanors is the basis of a great many impeachments for noncriminal abuse of power, Warren Hastings in 1787 being a prime example.
High crimes and misdemeanors is a phrase not unfamiliar to the founders because the American colonies and the early state governments had conducted impeachments of their own for acts that were non-criminal.
High crimes and misdemeanors is intentionally open (or vague), because it recognizes that one never knew in advance what form the royal urge to autocracy might take or what sort of devilry corrupt or ambitious officials might be up to.
High crimes and misdemeanors is a sturdy, familiar concept that was accepted into the Constitution as a compromise to George Mason between the overly limiting “treason or bribery” and the overly broad “maladministration”.
High crimes and misdemeanors is by no means limited only to technical crimes. Sometimes a high crime and misdemeanor is not a crime against forms, but against those eternal laws of justice, which are our rule and our birthright: offenses not in formal, technical language, but in reality, in substance and effect.
High crimes and misdemeanors is a term whose usage dates back to 1386 and has been used to impeach a great many officials for a wide variety of misconduct which wasn’t technically criminal.