Former FBI Director James Comey James Brien ComeyDemocrats fear Russia interference could spoil bid to retake Senate Book: FBI sex crimes investigator helped trigger October 2016 public probe of Clinton emails Trump jabs at FBI director over testimony on Russia, antifa MORE said Sunday that he wrote about three presidents in his new book, adding that two of them illustrated "ethical leadership."

"My book is about ethical leadership & draws on stories from my life & lessons I learned from others," Comey tweeted.

"3 presidents are in my book: 2 help illustrate the values at the heart of ethical leadership; 1 serves as a counterpoint. I hope folks read the whole thing and find it useful."

My book is about ethical leadership & draws on stories from my life & lessons I learned from others. 3 presidents are in my book: 2 help illustrate the values at the heart of ethical leadership; 1 serves as a counterpoint. I hope folks read the whole thing and find it useful. — James Comey (@Comey) April 15, 2018

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Comey did not identify the presidents he described.

His book, "A Higher Loyalty: Truth, Lies, and Leadership," will be released on Tuesday. Excerpts of it surfaced last week.

Comey compared Trump to a mob boss in the memoir, writing that Trump sought loyalty “like Sammy the Bull’s Cosa Nostra induction ceremony,” a reference to the infamous mob boss.