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(CNN) —  

Former FBI Director James Comey explained Thursday why he thinks “it’s possible” that the Russians could have compromising information about President Donald Trump.

Comey said that there are two data points about his interactions with the President that have prompted him to make the assertion – and the first is that “the President is constantly bringing it up with me to deny it.”

“In my experience as an investigator, it’s not an ironclad rule, but it’s a striking thing when someone constantly brings up something to deny that you didn’t ask about,” Comey said in a Thursday interview on CNN’s “The Lead with Jake Tapper.”

He clarified, “I think it’s unlikely, but I think it’s possible.”

The second reason that it’s possible the Russians might have “derogatory” information about Trump, Comey said, is that he was “struck” by how Trump “wouldn’t criticize Vladimir Putin even in private, which struck me as odd.”

The former FBI director added, “Now, those aren’t definitive, those aren’t conclusive facts, but the reason I say it’s possible is there are things that lead my common sense to believe it’s possible.”

Tapper pressed Comey, asking, “do you have evidence that President Trump is compromised by the Russians? Have you seen evidence of it?”

Comey responded by saying, “No. And I think I’ve said that throughout. I’m trying to be transparent. Here’s my reasoning, here’s why an honest answer has to be, ‘it’s possible.’”

Comey first made the explosive “it’s possible” remarks to ABC’s George Stephanopoulos in an interview on Sunday evening.

When Stephanopoulos asked Comey if he thinks “the Russians have something on Donald Trump,” the former FBI director responded, “I think it’s possible. I don’t know. These are more words I never thought I’d utter about a President of the United States, but it’s possible.”

The ABC interview kicked off Comey’s media blitz to promote the release of his new memoir, “A Higher Loyalty.” The book paints a highly critical picture of the President.

Trump has lashed out at Comey throughout the book tour, hurling insults at the former FBI director on Twitter and even suggesting that he should be jailed. White House press secretary Sarah Sanders said ahead of Comey’s book release that the former FBI director “will be forever known as a disgraced partisan hack.”