Former Acting FBI Director Andrew McCabe started the obstruction of justice and counterintelligence investigations involving President Donald Trump and his ties to Russia because he wanted to ensure the probe was on “solid ground” in case he was fired.

McCabe said in an interview to air on CBS’s “60 Minutes” Sunday that he took the action after speaking to Trump hours after the president fired his boss, former FBI Director James Comey, in May of 2017.

“I was speaking to the man who had just run for the presidency and won the election for the presidency and who might have done so with the aid of the government of Russia, our most formidable adversary on the world stage,” McCabe said in an excerpt aired on CBS on Thursday. “And that was something that troubled me greatly.”

McCabe was fired last March just 26 hours before he was scheduled to retire without a full pension. Then-Attorney General Jeff Sessions fired McCabe over allegations he had violated the FBI and Justice Department’s policy related to disclosures to the media. He’s responded that he was the target of a political attack by Trump.

“I was very concerned that I was able to put the Russia case on absolutely solid ground and in an indelible fashion” McCabe said in the interview. “That were I removed quickly or reassigned or fired, that the case could not be closed or vanish in the night without a trace.”

CBS’s Scott Pelley said McCabe discussed DOJ meetings shortly after Comey’s firing in which Deputy Attorney General Rod Rosenstein discussed possibly wearing a wire when talking to Trump about whether the vice president and Cabinet could invoke the Constitution to remove the president from office. The Justice Department in a previous statement claimed that Rosenstein was being sarcastic, but McCabe said he repeated it more than once and the suggestion was taken seriously.

“There were meetings at the Justice Department at which it was discussed whether the vice president and a majority of the Cabinet could be brought together to remove the president of the United States under the 25th Amendment,” Pelley said on the show. “These were the eight days from Comey’s firing to the point that Robert Mueller was appointed special counsel. And the highest levels of American law enforcement were trying to figure out what do with the president.”

McCabe has written a book, called “The Threat: How the FBI Protects America in the Age of Terror and Trump,” in which he writes about the 2016 election and its aftermath, in addition to his career at the FBI.

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