On Wednesday, Trump revoked Brennan's security clearance, which had allowed the ex-spymaster to continue to access classified documents since he resigned last January.
It was clear from the start that Trump's move was about punishing his critics and threatening other intelligence officials to watch what they say. But Trump did not order a review of the clearance held by former national security adviser Mike Flynn, who was sacked from the White House for lying to Vice President Mike Pence about his conversations with Russian officials and later pleaded guilty to lying to the Federal Bureau of Investigation.
The statement was dated July 26.
The Brennan dust-up reminds me of the Omarosa feud, oddly enough, in that both are examples of Trump counterproductively elevating a critic because he couldn't resist the temptation to take a swing at them. Given Trump's fondness for NDAs, I wonder if the next step will be to add nondisparagement clauses to all executive-branch security clearance applications.
The Trump administration stripped the retired intelligence official of his security clearance, which the president suggested was punishment for Brennan's criticism, and the "Morning Joe" analyst said those warnings rose above partisan jabs.
After Trump held a press conference with Russian President Putin in Helsinki last month Mr Brennan tweeted: "Donald Trump's press conference performance in Helsinki rises to and exceeds the threshold of "high crimes and misdemeanours".
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A former Central Intelligence Agency deputy director, John McLaughlin, speaking on MSNBC after Sanders read out the names, said, "the message that goes out is be careful what you say" about Trump.
Brennan has been extremely critical of the president.
Former secretary of state John Kerry accused Trump of "putting personal petty politics ahead of patriotism and national security".
But the tweets and statements made on MSNBC were not just critical in nature but in some cases accused Trump of treason and alluded to unverified rumors that Russian Federation was blackmailing Trump.
Then Sanders read a list of names: James Clapper, James Comey, Michael Hayden, Sally Yates, Susan Rice, Andrew McCabe, Peter Strzok, Lisa Page, Bruce Ohr.
The threat to pull his security clearance, Clapper added, will not silence him.
He continued, "I am very anxious about the message that it appears that Mr. Trump is trying to send to others, including those that now hold security clearances within the government".
Senator Mark Warner, the top Democrat on the Senate intelligence committee, warned that a "dangerous precedent" is being set.