The beauty of “high Crimes and Misdemeanors” from the perspective of the men of 1787 was that it provided both flexibility and some measure of guidance. Flexibility because it plainly pointed to the parliamentary practice of defining impeachable conduct on a case-by-case basis. Guidance because it incorporated, by reference, 400 years of prior practice on which one could rely in identifying the kinds and degrees of misbehavior that ought to be impeachable.
Moreover, the founders, both during the ratification period and afterward, identified multiple noncriminal acts they believed to be impeachable. At the Virginia ratifying convention, James Madison and Wilson Nicholas said abuse of the pardon power would be impeachable. Impeachment, some founders said, would also follow from receipt of foreign emoluments or presidential efforts to secure by trickery Senate ratification of a disadvantageous treaty. During the first Congress of 1789, Madison even argued that presidents could be impeached for “wanton removal of meritorious officers.”
In the Federalist Papers, Alexander Hamilton made the larger point that impeachment is directed at “political” offenses that “proceed from … the abuse or violation of some public trust.” He was echoed by the foremost of the first generation of commentators on the Constitution, Justice Joseph Story, who observed in his 1833 treatise Commentaries on the Constitution that impeachable conduct is often “purely political,” and that “no previous statute is necessary to authorize an impeachment for any official misconduct.”