Richard Nixon would have told Donald Trump he had overstepped his powers and risked impeachment if he ordered the prosecution of Hillary Clinton and the FBI chief James Comey, a former top lawyer to the disgraced late president has said.

“This is the sort of stuff of a banana republic,” John Dean, White House counsel to Nixon, said of a report late on Tuesday that Trump had to be talked out of commanding the justice department to bring charges against the two, whom he saw as his political enemies.

“If I had to channel a little of Richard Nixon, I think he’d tell this president he’s going too far. This is what an autocrat does,” Dean said on CNN on Tuesday night.

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He added: “This is a level that Richard Nixon never went to, where you went after somebody’s personal wellbeing by a criminal prosecution.”

Dean said that while Nixon broke the law by his involvement in the Watergate scandal, resulting in the president’s resignation in 1974, the idea that Trump would try to get Clinton and Comey prosecuted, as the New York Times reported late Tuesday, amounts to “really very, very heavy sledding”.

“I never heard him do it [break the law] by turning on his enemies and trying to put them in jail,” Dean said of Nixon.

Trump told the then White House counsel, Don McGahn, in the spring of 2018 that he wanted a criminal investigation of Hillary Clinton over her use of a private email server while secretary of state, and against Comey alleging a leak of classified material, the Times said, citing two unnamed people familiar with the conversation.

McGahn reportedly had a memo drawn up attempting to dissuade Trump, noting that the potential consequences for such an action could include impeachment. It is not clear if Trump read the memo, but he did not order such a move by the DoJ, although he apparently continued to mention in private his desire to prosecute the two.

Trump fired Comey in May 2017 and appointed Christopher Wray to replace him.

But the account of Trump exploring options to order the DoJ to prosecute Clinton and Comey or appoint a special counsel to investigate them brings into further stark relief his decision the day after the midterm elections to fire the attorney general, Jeff Sessions, and name a loyalist, Matt Whitaker, as acting attorney general with the assumption from the White House that he would now oversee the Trump-Russia investigation by Robert Mueller. Sessions had recused himself, leaving the deputy attorney general, Rod Rosenstein, overseeing Mueller, much to the chagrin of Trump.

“It’s not news that Trump wants DOJ to investigate or prosecute Clinton or Comey,” Harvard law professor Jack Goldsmith tweeted on Tuesday night. “He’s long expressed that opinion on Twitter and elsewhere … The President has nearly complete formal authority over DOJ. But the remarkable lesson of the last 2 years is that Trump nonetheless has practically no effective authority to use these tools to harm his political enemies. When it comes to using DOJ, Trump is incompetent and weak.”

“Jack’s got a point,” replied the Georgetown University law professor Marty Lederman.

“More importantly,” wrote Lederman, Trump’s influence presumably is now stronger, with [acting attorney general Matt] Whitaker in place.”

Former top FBI lawyer Jim Baker, a friend of Comey, wrote in Lawfare, a legal blog published in cooperation with the Brookings Institution, that the House judiciary committee concluded Nixon’s close contact with officials in the DoJ when it was investigating Watergate amounted to an impeachable misuse of executive power.