It’s hard to find defenders of impeachment—or at least, it’s hard to find good faith, consistent defenders of impeachment.

Just look at former House Speaker Newt Gingrich, who once voted to impeach President Bill Clinton for obstruction of justice, only to recently assert that it’s impossible for a president, and in particular Donald Trump, whom he supports, to obstruct justice. Most of the hypocrisies are more garden variety. When Republicans seek to impeach a Democratic president, Democrats howl that it’s unscrupulous naked politics; when a Republican is in the White House, Democrats rediscover the value of impeachment, while the GOP suddenly recognizes its recklessness.

Recent debates on this topic aren’t a symptom of a newly polarized age, and they aren’t a sign of national decline, the Harvard legal scholar (and former Obama adviser) Cass Sunstein said Wednesday at the Aspen Ideas Festival, which is co-hosted by the Aspen Institute and The Atlantic.

“The very word impeachment sounds kind of unfamiliar and British and dusty,” he quipped, but in fact, impeachment is a fundamental part of the American project, spanning back to the Declaration of Independence, which stands as articles of impeachment for King George. Yet despite this integral role, impeachment remains little understood, even among top political leaders, with the result that most of the articles of impeachment brought against American presidents have been somewhere between legally dubious and grievously wrong—and so have some of the comments made about the prospect of impeaching President Trump.

Even before the American Revolution, colonial politicians had begun resuscitating the idea of impeachment, a 14th-century English legal concept that had become moribund. John Adams argued even before the war that impeachment was a fundamental right of British subjects. The problem with a monarchy, after all, was that the people couldn’t revoke consent to be governed by him or, occasionally, her. The revolution was a way of putting that into practice.

“The famous ‘shot heard around the world’ was a gun, but the initial shots heard round the world were impeachments by the American democratically elected legislators of followers of the crown who were executing the orders of the crown,” Sunstein said.

But the formulation in the U.S. Constitution—providing for impeachment in the case of “treason, bribery, or other high crimes and misdemeanors”—is the somewhat opaque product of a debate in the Constitutional Convention. Alexander Hamilton’s successful advocacy for a unitary executive produced a backlash among delegates who feared the creation of a new monarch. Impeachment was the essential safety valve.

How to structure it, though? Roger Sherman’s suggestion of a Senate that could impeach a president for any reason was rejected for making the presidency too precarious. A counterproposal allowing for impeachment in cases of “maladministration” was found to be too vague. There’s no record of further discussion of the final terms at the convention, but in the Federalist Papers, Hamilton offered some clarification, writing that impeachable offenses were those that concerned “the abuse or violation of some public trust. They are of a nature which may with peculiar propriety be denominated political, as they relate chiefly to injuries done immediately to society itself.”

That’s central, Sunstein said, because it makes clear two important points about when impeachment is proper: First, it need not require an actual crime; and second, it is primarily about gross neglect or abuse of power. If that is true, the complaints, sometimes voiced by pearl-clutching pundits, that impeachment might be “politicized” seems almost laughable. But it also means that much of the (very early) debate about impeaching Trump is fought on questionable grounds.

“[House Minority Leader Nancy] Pelosi made a terrible blunder in saying relatively recently that the question is whether the president has committed a crime,” Sunstein said. “That is not the question.”

It also means that of the several articles of impeachment brought or nearly brought against American presidents, most of them fail to meet the Founders’ test. Andrew Johnson was impeached for firing Cabinet members, a move that violated an act of Congress that Johnson sincerely (and correctly) believed was an unconstitutional infringement on the separation of powers. Even if he had been wrong, Sunstein said, Johnson should not have been impeached for a good faith move.

Richard Nixon nearly faced four counts. One failed count, for tax evasion, was completely inappropriate, Sunstein argued: Though an obvious violation of law, it had no bearing on Nixon’s conduct of the presidency. A second charge, for resisting subpoena, is possibly but not necessarily valid, since a president could have good reasons to resisting a subpoena. A third is more debatable: Nixon was charged with covering up the Watergate break-in. Nixon might have been more fairly prosecuted for overseeing the burglary, Sunstein argued, but nabbing him for trying to use the federal government to commit the cover-up was “probably good enough.” Only the fourth charge, of using the federal government’s muscle to prosecute political enemies, is a clear slam-dunk under the Founders’ principles.

Of course, minding the history of impeachment is important, but there’s a far more pressing question for many citizens today: Whither Trump? Sunstein, having scolded legal colleagues for playing pundit, was reluctant to address the question directly. Setting aside the impossibility of impeaching Trump under the present circumstances of GOP control of Congress, Sunstein said he was wary of trying to remove the president simply for being bad at his job. Nonetheless, he said Trump’s prolific dishonesty might form a basis for trying to remove him.

“If a president lies on some occasions or is fairly accused of lying, it’s not impeachable—but if you have a systematic liar who is lying all the time, then we’re in the ballpark of misdemeanor, meaning bad action,” he said.

Sunstein seemed somewhat surprised to be discussing the very idea of removing a president. “If you told me as late as December 2016 that I’d actually be working on the topic of impeachment I would have thought it was more probable that I was trying out for the Olympic equestrian team,” he said. Given the topicality of impeachment, he is neither riding a live horse nor beating a dead one.