'A Man Without Courage': Dershowitz Slams Comey for Leaking Trump Memos

Republican National Committee spokeswoman Kayleigh McEnany ripped James Comey for his "assault" on President Trump, declaring that the former FBI director "can't be trusted."

Ahead of the release of his tell-all book, Comey has been extremely outspoken in his criticism of the president.

In an interview with ABC News’ George Stephanopoulos, Comey said Trump is "morally unfit" to be president and compared him to a "mob boss."

"He is going around, spewing lies, defaming this president's character and marginalizing GOP voters everywhere," McEnany told Harris Faulkner on "Outnumbered Overtime." "For Jim Comey to go in from day one taking notes about this president ... really not giving him a chance, I think it undermines GOP voters, no doubt about it."

She said Comey is just trying to sell more copies of his book, "A Higher Loyalty," and he has legitimate credibility issues that even Democrats -- including Senate Minority Leader Chuck Schumer (D-N.Y.), House Minority Leader Nancy Pelosi (D-Calif.) and Sen. Bernie Sanders (I-Vt.) -- have called out.

"Both sides are questioning this man's credibility. And that should tell you all you need to know about Jim Comey. He cannot be trusted. And that interview last night was a bunch of lies against this president," McEnany said.

She said that's why the RNC launched the website LyinComey.com, to document untrue statements Comey made before Congress and to compile Democrats' extensive criticism of him.

Bongino Rips Comey for Trump 'Mob Boss' Comparison: 'He's an Embarrassment to the FBI'

Napolitano: Comey Comment on Obstruction Is 'Dangerous' for Trump

Christie: Comey 'Would Have Fired Me on the Spot' If I Did What He Did