Former CIA Director John BrennanJohn Owen BrennanWebb: Questions for Robert Mueller A brief timeline of Trump's clashes with intelligence director Dan Coats Trump critic Brennan praises his Iran decision: I 'applaud' him MORE on Friday went after President TrumpDonald John TrumpO'Rourke: Trump driving global, U.S. economy into recession Manchin: Trump has 'golden opportunity' on gun reforms Objections to Trump's new immigration rule wildly exaggerated MORE over his attacks on former FBI Director James ComeyJames Brien ComeyBarr predicts progressive prosecutors will lead to 'more crime, more victims' James Comey shows our criminal justice system works as intended Trump says he's 'very strongly' considering commuting Rod Blagojevich's sentence MORE, tweeting that Trump’s “kakistocracy is collapsing after its lamentable journey.”

“As the greatest Nation history has known, we have the opportunity to emerge from this nightmare stronger & more committed to ensuring a better life for all Americans, including those you have so tragically deceived,” Brennan tweeted at Trump.

A kakistocracy is a form of government in which the worst persons are in power.

Brennan has been a regular critic of Trump, warning last month that lawmakers who protect him will face "a reckoning."

If anything, his criticisms have become more pronounced in the last few months. 

Trump lashed out at Comey in a pair of tweets early Friday, calling him a “leaker & liar” and an “untruthful slime ball.” 

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The attack came after multiple media outlets reported on excerpts of Comey’s upcoming book.

Comey writes in the book that Trump had asked him to probe the infamous “pee tape” mentioned in the so-called Steele dossier in order to disprove its existence. The dossier alleges that Trump hired prostitutes to urinate on a bed used by former President Obama and first lady Michelle ObamaMichelle LeVaughn Robinson ObamaMichelle Obama to present Lin-Manuel Miranda with the Portrait of a Nation Prize Michelle Obama thanks her high school for naming new athletic complex after her US ambassador to Germany calls out journalists who blocked him on Twitter MORE at the Moscow Ritz-Carlton.

Comey also ripped Trump as "untethered to truth" in the book and compared him to a mob boss.

“A Higher Loyalty: Truth, Lies, and Leadership” comes out Tuesday.