WASHINGTON – In the more than 50 years since the Constitution was amended to create a way to remove a president unable to do his job, the process has never been triggered.

But the former acting director of the FBI says officials thought about it.

Andrew McCabe told "60 Minutes" in an interview that top Justice Department officials discussed whether Vice President and a majority of the cabinet would be willing to invoke the 25th Amendment to remove President Donald Trump from office.

"They were counting noses," 60 Minutes' Scott Pelley told "CBS This Morning" in a preview of his interview with McCabe that will air Sunday. McCabe, who was fired by then-Attorney General Jeff Sessions last year, has written a book coming out next week, "The Threat: How the FBI Protects America in the Age of Terror and Trump."

After news of McCabe's comments broke Thursday, tweeted that McCabe is "a disgrace to the FBI and a disgrace to our Country."

And Vice President Mike Pence called "any suggestion" of triggering the amendment "absurd," according to NBC News reporter Andrea Mitchell, who spoke with him while traveling in Europe. She quoted him as saying, "I could not be more proud to stand with him and the words or writings of a disgraced FBI agent won’t change that fact for the American people."

McCabe took over as acting FBI director after Trump fired James Comey in 2017. Sessions fired McCabe after concluding that he had misled internal investigators. The Justice Department disputed McCabe's characterization of discussions about the 25th Amendment, but did not deny that they had taken place.

What is the 25th Amendment?

The amendment, ratified in 1967, created a legal mechanism for designating a head of state when the president is disabled or dead. It also formalized the historical practice for the vice president to permanently take over if the president dies or resigns, and gives the president and Congress shared power to replace a vice president.

Why was it written?

John F. Kennedy’s assassination brought renewed interest to presidential succession questions. Lyndon B. Johnson’s ascension to the presidency meant that – for the 16th time – the country had no vice president. And there was no tested way of dealing with a severe presidential illness. Johnson previously had suffered a heart attack and the next two people in line to be president were the 71-year-old speaker of the House and the 86-year-old president pro tempore of the Senate.

Has it been used before?

Gerald Ford followed the first two sections of the amendment when becoming Richard Nixon’s vice president after Spiro Agnew resigned, and when becoming president after Nixon’s resignation. The amendment’s third section, which allows for a president to temporarily cede power and duties to a vice president, was used once after Ronald Reagan underwent surgery in 1985 and similarly when George W. Bush was under anesthesia in 2002 and 2007.and twice when George W. Bush underwent surgery under general anesthesia. The fourth section, a process for removing a president when others believe he is “unable to discharge the powers and duties of his office,” has never been used.

When did the author intend the 4th section to be invoked?

Former Sen. Birch Bayh wrote in his book “One Heartbeat Away: Presidential Disability and Succession” that he knew the most controversial aspect of the amendment he authored would be how to handle the rare instances when a president’s team disputed his ability to serve.

“You know, fellows, we've talked about this problem a hundred times,” Bayh recounted telling his aides when they were in the final stages of negotiation. “The only time it would present itself – the only time the president would say 'I'm well and able' and the vice president and cabinet would disagree – would be if the president was as nutty as a fruit cake.”

Why is it being talked about now?

The amendment got new attention after President Donald Trump's inauguration and re-emerged as a top talker after some of Trump's controversial comments and actions, or because of inside reports about the workings of the White House.

In 2017, for example, Trump triggered questions about his stability when he tweeted he has a bigger "nuclear button" than Kim Jong Un of North Korea.

Michael Wolff’s “Fire and Fury,” published last year, painted a picture of a president not up to the job.

“It's not unreasonable to say this is 25th Amendment kind of stuff,” Wolff said in NBC’s "Meet the Press" appearance.

In Bob Woodward's book "Fear: Trump in the White House", then-White House chief of staff John Kelly calls Trump "an idiot" who has "gone off the rails."

In an opinion piece published by The New York Times last year, the anonymous author wrote that Cabinet members had "whispered" about invoking the 25th Amendment because of Trump's increasing erratic behavior.

Soon after, The New York Times reported that Deputy Attorney General Rod Rosenstein discussed invoking the 25th Amendment when the White House had been plunged into chaos after the firing of FBI Director James Comey. The report said Rosenstein suggested wearing a wire during encounters with the president while proposing the recruitment of other administration officials to support the president's removal.

Rosenstein called the story "inaccurate and factually incorrect."

In the "60 Minutes" interview airing Sunday, McCabe said the suggestion came up more than once and was so serious it was discussed with FBI lawyers, Pelley told "CBS This Morning."

How could the 25th Amendment be triggered?

The vice president and a majority of the Cabinet could declare the president unable to “discharge the powers and duties of his office.” If the president disputes that determination, two-thirds of both the House and the Senate must vote to put the vice president in charge.

In addition, lawmakers can designate through legislation an alternative group – other than the Cabinet – that the vice president could work with to declare a president unable to serve.

Is the amendment clear on what qualifies as an inability to serve?

No. And Jay Berman, one of the Bayh aides who worked on the amendment, said that was intentional.

“It didn’t settle the issue of what it is,” he said in an interview. “It provided a mechanism for addressing the issue.”

Would a psychiatrist or other doctor need to weigh in?

Bayh assumed the vice president would consult with medical experts, but the drafters never felt comfortable that the decision would be made solely by a group of doctors, according Berman. Section 4 was not intended to overturn the verdict of the electoral system, or to be a substitute for impeachment, Berman said.

“It was certainly on our mind that the impeachment proceeding was still something that was available in the case of a president that had violated his oath or hadn’t performed his duties,” he said. “That truly should be the first line of defense in any case where there’s an issue about removing the president.”

Is it likely to be used?

The anonymous senior official who wrote the New York Times opinion piece said discussions of invoking the amendment didn't go farther than the early whispers.

"No one wanted to precipitate a constitutional crisis," the author added. Instead, officials are trying to to "do what we can to steer the administration in the right direction until – one way or another – it’s over."

In his statement last fall denying that he suggested wearing a wire, Rosenstein also said he wanted to be clear that "based on my personal dealings with the president, there is no basis to invoke the 25th Amendment.”

Plus, Pence has given no indication that he questions Trump’s ability to be president.