In 1827 President James Madison published the notes he took during the 1787 Constitutional Convention. Madison’s notes show some delegates did not want a clause for impeachment of the president. Some delegates wanted the grounds for impeachment to be enumerated and specific. Other delegates wanted the clause to enable impeachment and removal from office for more general offenses.
They settled on a mix of specific and general. Article 2, Section 4 of the US Constitution states the president shall be removed from office for the crimes of “Treason, Bribery, or other High Crimes and Misdemeanors.”
Treason is defined in Article 3, Section 3, Clause 1. Bribery is not defined in the Constitution but the crime long existed in English and American Common Law. The phrase “other High Crimes and Misdemeanors” is left undefined.
Benjamin Franklin is recorded in Madison's notes favoring general grounds of impeachment. Madison quotes Franklin saying the president should be removed from office when when he has “rendered himself obnoxious”.
The first article of impeachment should be, “He has rendered himself obnoxious”.