On one extreme is the position enunciated by then Rep. Gerald Ford, and now championed (if that's the word I want) by Maxine Waters: Impeachable offenses are anything Congress says they are. Here's how Ford put it:
What, then, is an impeachable offense? The only honest answer is that an impeachable offense is whatever a majority of the House of Representatives considers it to be at a given moment in history; conviction results from whatever offense or offenses two-thirds of the other body considers to be sufficiently serious to require removal of the accused from office. . . .”
Most scholars don't go to that extreme, but a common position is that the phrase "high ... misdemeanors" includes non-criminal acts that somehow constitute an abuse of office. Or something. That's the position of Jonathan Turley, the law professor from GWU whom the GOP called to testify in the House regarding impeachment. Turley is a leading authority on impeachment, in both the field of theory as well as of practice, and his grasp of the complications is apparent in his prepared statement to the House, which runs to 53 pages (and, yes, I did read it all).
While Turley is adamant that a president may be impeached for non-criminal acts, it develops that he does have reservations--in effect, he appears to regard an impeachment based solely on non-criminal charges to be, if not exactly invalid, then at least to be a very bad idea.
Another noted law professor, now emeritus, who has written extensively in a popular format on the subject of impeachment is Alan Dershowitz. Dershowitz's views are widely derided, especially by his erstwhile liberal friends. His views could be said to run to the opposite extreme (if truth can ever be considered an extreme position) from those of Ford and Waters. For our purposes there are two elements to Dershowitz's position that interest us, although only the first will be discussed here:
1) Dershowitz strenuously maintains that a president may only be impeached for actual criminal acts which also constitute an abuse of office ("high crimes" not "low crimes"). With regard to the phrase "high ... misdemeanors" he maintains that misdemeanors in this sense are "a species of crime."
2) Dershowitz points to the Constitutions stipulation that the Chief Justice shall preside at the Senate trial of a president (but not of lesser officials) as indicating that the Judicial Branch of government was expected to play a more active role in presidential impeachments--in effect, all three branches of government would be involved in so momentous an event.
Many of Dershowitz's writings on impeachment can be found collected in The Case Against Impeaching Trump. The virtue of Dershowitz's views should be obvious. His position provides a clear standard for what is or is not an impeachable offense, thus providing predictability and stability in the political sphere of public life that otherwise might degenerate, as Hamilton feared, into raw partisan brawling. His views on the potential role of the Judicial Branch offer further control over the impeachment process. For brief presentations of his views, here are three articles:
Rob Natelson, a retired professor of constitutional law, has an article on impeachment out today that expands on his previously expressed views, focusing in particular on the notion of "high ... misdemeanors." The article is What the ‘Expert’ Panel Should Have Told You About Impeachment—But Didn’t. Natelson doesn't mention Dershowitz and doesn't address the issues in the same terms, but I believe his views are broadly compatible with those of Dershowitz and can be seen as presenting a somewhat more refined version of Dershowitz's view on the nature of "high ... misdemeanors." As you'll see, Natelson's historical research strongly indicates that "high ... misdemeanors", as the concept evolved, are to be understood as crimes. Or, as Dershowitz says, "a species of crimes."
What follows is a much abridged and somewhat reformatted extract from his article. When you've read it I think you'll have a clear idea of why Professors Turley and Dershowitz, among others, are so adamant that the case against Trump is abusive of the Constitution and harmful to our polity:
This short essay does what the House Judiciary Committee’s panel of “expert witnesses” did not successfully do.
First, it explains the meaning of the Constitution’s “high Crimes and Misdemeanors” standard.
Next, it discusses how that standard applies to President Donald Trump’s interactions with Ukrainian President Volodymyr Zelensky.
Finally, it details the kind of evidence the House Judiciary Committee should gather to determine whether the president committed an impeachable offense.
Many phrases in the Constitution—such as “necessary and proper,” “Privileges and Immunities,” and “Convention for proposing Amendments”—carry specialized 18th century meanings not obvious to the modern reader. Recall that most of the leading Founders were lawyers and the Constitution is a legal document. Some of these phrases derive from 18th century law.
Therefore, to understand them you have to consult 18th century legal materials in addition to better-known sources such as the 1787 convention debates or the Federalist Papers.
Unfortunately, most of the scholars called by the House Judiciary Committee to address the meaning of “high Crimes and Misdemeanors” were not able to do so accurately.
According to the authoritative Westlaw database, two of the three Democratically appointed witnesses have published no scholarly work on impeachment: Their specialties are in other areas. None showed any familiarity with 18th century fiduciary standards—which (as explained below) are part of the law of impeachment. All of the witnesses voted against President Trump, and several have been involved in anti-Trump activity.
It’s not surprising, therefore, that, except for professor Jonathan Turley’s heavily footnoted 53-page written statement, the testimony was biased and superficial.
What Is the Standard?
Impeachment law is not for amateurs. It rests on English parliamentary history extending at least as far back as the 1300s. Furthermore, impeachment standards evolved over time. To understand the Constitution’s rules we must know what the standards were when the Constitution was adopted. We can do so by consulting 18th century parliamentary records and legal materials.
Here’s some of what they tell us:
The term “high Crimes” means, approximately, “felonies.”
The phrase “high … Misdemeanors” refers to what the founding generation called “breach of trust” and what modern lawyers call breach of fiduciary duty. Fiduciary duties are the legal obligations imposed upon those who manage the affairs of other people—bankers, corporate executives, accountants, guardians, and so forth. In broad outline, fiduciary law when the Constitution was adopted was similar to what it is today.
In the 14th and 15th centuries, an official could be impeached because Parliament disagreed with his policy decisions. However, as several American Founders recognized, by the 18th century this was no longer true. ...
The trial in the upper house of the legislature was a judicial proceeding, not primarily a political one. As the 1782 edition of the popular Jacob’s Law Dictionary noted, “the same evidence is required in an impeachment in Parliament, as in the ordinary courts of justice.” The hearsay and impressionist evidence gathered by the House Intelligence Committee is not admissible.The core of the case against President Trump is that he used his political position to seek re-election assistance from a foreign government. Although there’s dark talk of crimes committed, the principal charge is fiduciary rather than criminal. In other words, a “high … Misdemeanor.”
House Democrats have struggled to define Trump’s alleged offense. Initially, they described it as “quid pro quo.” Then they employed the term “bribery.” The legally correct designation is “self-dealing.”
Self-dealing is betraying your employer’s interests to enrich yourself. It’s a violation of the fiduciary duty of loyalty.
We can assume the president might benefit from a Ukrainian investigation, but that doesn’t mean asking for an investigation was self-dealing as defined by fiduciary, and therefore by impeachment, law. There’s nothing unusual or improper about a president asking a recipient of U.S. foreign aid to address corruption. As for seeking political advantage: If we punished every politician who did that, they would all be swinging from the yardarm.
This is as true in foreign as in domestic affairs. When President Barack Obama told the Russian president he would have more flexibility after his re-election, he was saying (1) an agreement now would benefit both Russia and the United States, but (2) I’m going to sacrifice our mutual interests for the present because such an agreement might hurt my re-election campaign. Was this impeachable self-dealing? Almost certainly not.
So where is the divide between “normal” conduct and impeachable conduct? To answer this, we need to weigh at least three factors: impeachment precedent, the national interest, and the practice of other presidents.
An 18th century impeachment treatise outlines the specific facts by which several officials were impeached for what we now call self-dealing.
All these cases boil down to stealing public property. ...
Another part of the answer lies in whether President Trump violated the national interest. As a general rule, self-dealing generally is not just enriching yourself. It’s enriching yourself at the expense of your employer. ...
Despite Col. Alexander Vindman’s complaint that Trump violated “the consensus of the interagency,” the question of whether Trump acted contrary to the national interest is a difficult one to answer.
Perhaps we had a national interest in not asking President Zelensky to investigate. But we also had a national interest in asking, ...
Thus, you can argue the “national interest” issue both ways. It looks more a policy question than a clear case like theft of public funds.
Still another part of the answer lies in how similar officials act in similar circumstances. In absence of a crime, if you want to determine whether a banker handled funds properly, you should investigate how bankers usually handle funds. If you wish to determine whether an investment adviser gave reasonable advice, you should consult what other reputable advisers recommend in the same circumstances.
Similarly, to decide whether President Trump engaged in impermissible self-dealing, we need testimony about how other officials conduct themselves. We know, for example, that then-Vice President Biden explicitly made aid to Ukraine conditional on firing a Ukrainian prosecutor. If that conduct wasn’t impeachable (and I don’t believe it was) then Trump’s more tepid conduct certainly isn’t impeachable.