Alan Dershowitz, the Harvard Law School professor emeritus, civil libertarian and defender of Donald Trump, wants the public to know he hasn't changed his mind on what makes an impeachable offense. He's just got a deeper understanding of history, he maintains now, ever since he declared, during the Bill Clinton impeachment trial, that impeachable conduct does not require a crime.

"It certainly doesn't have to be a crime," Dershowitz said in a 1998 media interview. "If you have somebody who completely corrupts the office of the president and abuses trust and who poses great danger to our liberty, you don't need a technical crime."

Dershowitz has arguably changed his tune now, saying now that impeachment requires a "criminal-like" violation. "I am much more correct right now, having done more research," Dershowitz told CNN's Anderson Cooper on Monday. "I didn't do the research back then. I wasn't wrong. I am just far more correct now than I was then." Dershowitz, a member of the Trump impeachment defense team, said he has a "more sophisticated basis for my argument now."

Dershowitz asserted Monday night on Twitter: "There is no inconsistency between what I said during the Clinton impeachment and what I am saying now. I said then that there doesn't have to be a 'technical' crime. I have said now there must be 'criminal-like' conduct, or conduct 'akin to treason and bribery.'"

The dispute isn't entirely academic. Trump's lawyers asserted in their impeachment trial brief, filed on Monday, that "the Framers restricted impeachment to specific offenses against 'already known and established law.'" That argument, however, cuts against a broad consensus among legal scholars that impeachment doesn't require a specific criminal offense but, rather, and far more broadly, an abuse of public trust. Dershowitz is expected to grab a speaking role at Trump's trial later this week.

Pat Cipollone White House Counsel Pat Cipollone. Photo: Diego M. Radzinschi/ALM

Trump's impeachment lawyers, led by White House Counsel Pat Cipollone and Jay Sekulow, used their opening trial brief largely to attack the impeachment process, calling it "rigged." The defense team claimed the president had done nothing wrong in his communication with the president of Ukraine, a central focus of the articles of impeachment. House Democrats contend Trump abused the power of his office in pressuring Ukraine to announce investigations of his election rivals, a move that would have benefited Trump personally.

Here's a snapshot of some of the things lawyers are saying about the Trump impeachment brief:

>> Frank Bowman, law professor at University of Missouri and an impeachment scholar: "This argument is constitutional nonsense. The almost universal consensus—in Great Britain, in the colonies, in the American states between 1776 and 1787, at the Constitutional Convention and since—has been that criminal conduct is not required for impeachment." [NYT]

>> George Conway, Wachtell, Lipton, Rosen & Katz and husband of Kellyanne Conway: "Even if a statutory crime were required, the House's charge that Trump tried to solicit a personal benefit (Ukraine's announcement of an investigation) in exchange for an official act (releasing the security aid) constitutes bribery, both as understood in the Framers' time and under the federal criminal code today." [The Washington Post]

>> Lawrence Tribe, impeachment scholar and professor at Harvard Law School: "The argument that only criminal offenses are impeachable has died a thousand deaths in the writings of all the experts on the subject, but it staggers on like a vengeful zombie. In fact, there is no evidence that the phrase 'high Crimes and Misdemeanors' was understood in the 1780s to mean indictable crimes." [The Washington Post]

>> Orin Kerr, law professor at University of California-Berkeley: "Should be a simple rule: Profs repping clients are lawyers, not profs. Leave all academic labels and affiliations behind." [Twitter]

Jerry Nadler Rep. Jerry Nadler, D-New York, chairs a House Judiciary Committee Department of Justice oversight hearing in February. Credit: Diego M. Radzinschi /ALM

>> Rep. Jerry Nadler, a House impeachment manager: "Now, when I saw Professor Dershowitz's comment that you have to have a violation of the criminal code to be in abuse of power, to be constitutionally suspect, to be constitutionally impeachable. I thought he was merely ignorant, now that I see his 1999 quote, I know he's lying." [MSNBC]