This article is a couple of years old, but very relevant to the current discussion of whether impeachment requires a statutory crime. This is really good reading!
“The 1974 House Judiciary Committee put the British example favored by Mason to use during Nixon’s Watergate scandal. “High crimes and misdemeanors,” the committee’s staff report argued, originally referred to “damage to the state in such forms as misapplication of funds, abuse of official power, neglect of duty, encroachment on Parliament’s prerogatives, corruption, and betrayal of trust,” allegations that “were not necessarily limited to common law or statutory derelictions or crimes.”
The committee approved three articles of impeachment against Nixon on these grounds, charging him with obstructing justice and subverting constitutional government. The full House never voted on impeachment, but the proposed articles helped force the president’s resignation two weeks later.
When Madison, Mason, and Randolph reunited in Richmond in June 1788 for Virginia’s convention to ratify the Constitution, they continued their debate on the question of impeachable offenses. By then each man had taken a different position on the Constitution. Madison had emerged as its main architect and champion, and Mason as a leading opponent who declared “it would end either in monarchy, or a tyrannical aristocracy.” Randolph, meanwhile, had voted against the Constitution in Philadelphia in September 1787, but swung his vote to yes in 1788 after eight other states had ratified it. Their disagreement illuminates the discussion over presidential powers in the modern era.
When Mason argued that “the great powers of Europe, as France and Great Britain,” might corrupt the president, Randolph replied that it would be an impeachable offense for the president to violate the Constitution’s emoluments clause by taking payments from a foreign power. Randolph was establishing that violations of the Constitution would constitute high crimes and misdemeanors – and so would betraying the U.S. to a foreign government.”