Washington (CNN) Legal scholars are panning new arguments championed by Harvard professor Alan Dershowitz, who recently joined President Donald Trump's legal team and is making the case that Trump cannot be impeached because he didn't commit any crimes.

In a series of interviews over the weekend, Dershowitz fleshed out his controversial views , which he said he'll present on the Senate floor during Trump's ongoing impeachment trial.

"I will be paraphrasing the successful argument made by (Supreme Court) Justice Benjamin Curtis in the trial of (then-President) Andrew Johnson back in the 1860s, where he argued that the framers intended for impeachable conduct only to be criminal-like conduct or conduct that is prohibited by the criminal law," Dershowitz said Sunday on CNN's "State of the Union."

"Without a crime, there can be no impeachment," Dershowitz said.

These comments echoed what other members of Trump's legal team included in their 171-page trial brief filed with the Senate on Monday, which claimed that the United States Constitution "makes clear that an impeachable offense must be a violation of established law."

CNN's chief legal analyst Jeffrey Toobin, who was one of Dershowitz's law students at Harvard, sparred with his former professor during a joint appearance on State of the Union.

"Every scholar, except you... that has looked at this issue, about whether it has to be a crime in order to be an impeachable offense, has said no," Toobin told Dershowitz, citing arguments that were first put forward by Alexander Hamilton and others in the Federalist Papers in the 1780s.

CNN legal analyst Ross Garber, one of the leading impeachment experts in the country, also rejected Dershowitz's reasoning. In recent years, Garber defended four Republican governors who faced potential impeachment, three of whom eventually resigned from office.

"I'm not sure of anybody who's defended more impeachments than I have, and even I think Dershowitz is wrong on this," Garber said Monday on CNN. "I don't think you need a technical criminal violation for there to be an impeachable offense, and there are lots of reasons for that."

One reason, Garber explained, was that there weren't many criminal statutes on the books when the Constitution was adopted. Another reason came from history, Garber said: The phrase "high crimes and misdemeanors," was used in England before the framers included it in the US Constitution, and it wasn't understood to require a criminal offense for impeachment.

Some of the experts who testified about constitutional grounds for impeachment at the House Judiciary Committee also agreed that a crime wasn't a prerequisite for removing a president.

University of North Carolina Professor Michael Gerhardt, a CNN contributor, told lawmakers that the Constitution "plainly does not" require proof of a crime, adding that, "everything we know about the history of impeachment reinforces the conclusion that impeachable offenses do not have to be crimes."

Even the scholar who was invited to testify by Republicans, George Washington University Professor Jonathan Turley, wrote in a November column in The Wall Street Journal that "it is true that impeachment doesn't require a crime." But he also testified that Trump's conduct with Ukraine wasn't impeachable and that all past presidential impeachments had proof of a crime.

"This would be the first impeachment in history where there would be considerable debate, and in my view, not compelling evidence of the commission of a crime," Turley told lawmakers.

Former independent counsel Robert Ray, another new addition to Trump's legal team, made the same case as Dershowitz in a CNN op-ed last year . Ray is part of the team that will present these arguments on Trump's behalf on the Senate floor.

"The point being that House Democrats, in this impeachment inquiry, have jettisoned treason, bribery, extortion, and foreign campaign contributions as a predicate, under law, for impeachment. Instead, we are left with abusive conduct and an interbranch dispute over witnesses and documents," Ray wrote. "The bar for impeachment has been lowered in an unprecedented way."

He was countered by CNN legal analyst Michael Zeldin, who endorsed the more broadly accepted view that a crime wasn't necessary.

With his arguments, Dershowitz signaled his support for legal theories that say the president has almost unquestionable power, a view that is shared by some leading conservative figures.

Allegations of flip-flopping

In the interviews, Dershowitz fended off accusations of flip-flopping, after old footage emerged of a 1998 interview on CNN where he said a crime wasn't necessary to remove a President.

That view is now being embraced by House Democrats, who approved articles of impeachment against Trump but didn't accuse him of any specific crimes. Instead, they charged him with abuse of power and obstructing Congress. (A separate House Judiciary Committee report said Trump committed bribery and "multiple federal crimes" by withholding US aid from Ukraine.)

"I had been consistent in my views on impeachment since the 1970s," Dershowitz said on State of the Union. "That's more than I can say for some of my other academic colleagues, who seem to be making their arguments based on partisan considerations."

In an interview with ABC's "This Week," Dershowitz identified himself as a "liberal Democrat" and said he voted against Trump in 2016, casting his ballot for Democratic nominee Hillary Clinton. He said he was defending Trump not because of politics but to protect presidential powers.

At least one expert came to Dershowitz's defense: Evan Mandery, a professor at the John Jay College of Criminal Justice who has published extensive profiles of Dershowitz for Politico.

Dershowitz is a "serious civil libertarian," Mandery said Monday morning on CNN. "I think his impulse is honest... I think he thinks he's coming from an intellectually consistent place."