President Trump will face an obstruction of justice charge from special counsel Robert Mueller, former Attorney General Eric Holder predicted.

“You technically have an obstruction of justice case that already exists,” Holder, who served under then-President Obama, said on HBO’s "Real Time with Bill Maher." "I've known Bob Mueller for 20, 30 years; my guess is he's just trying to make the case as good as he possibly can. So, I think that we have to be patient in that regard.”

Trump’s critics have speculated about an obstruction charge ever since he fired FBI Director James Comey in the midst of an investigation into potential ties between the Trump campaign and Russia. The president said he was frustrated that Russia-related allegations had become “an excuse for having lost an election,” and he was also apparently annoyed that Comey refused to say publicly that Trump himself was not under investigation, although Comey had made such comments in private.

“I have absolute right to do what I want to do with the Justice Department,” Trump told the New York Times in December 2017.

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It’s not the first time that Holder has suggested that an obstruction case could be made, though has stopped short previously of predicting Mueller would bring the charge. But Trump’s defenders maintain that he has the authority to dismiss the FBI director at any time.

"You cannot charge a president with obstruction of justice for exercising his constitutional power to fire Comey and his constitutional authority to tell the Justice Department who to investigate, who not to investigate,” Harvard Law professor Alan Dershowitz said in December. “That’s what Thomas Jefferson did, that's what Lincoln did, that's what Roosevelt did. We have precedents that clearly establish that.”

Such views have stoked Trump’s anger at Attorney General Jeff Sessions, who recused himself from oversight of the Russia investigation due to his own role on the Trump campaign. That decision paved the way for Deputy Attorney General Rod Rosenstein to appoint Mueller as special counsel after the Comey firing.

“I don’t want to get into loyalty, but I will tell you that, I will say this: Holder protected President Obama. Totally protected him,” Trump said in the New York Times interview. “When you look at the things that they did, and Holder protected the president. And I have great respect for that, I’ll be honest.”

Holder rejected the compliment. “The difference between me and Jeff Sessions is that I had a president I didn't have to protect,” he told Maher.

He also suggested that Sessions should resign rather than endure Trump’s public criticism. “At some point, though, you would hope that you would have the intestinal fortitude or the pride to simply say, you know, 'I wanted this job all my life, but it's not worth it, and I'm not going to take that kind of abuse, and I'm simply going to tell you, you know, go screw yourself, and I'm out,’” Holder said.

Maher replied that Sessions is “doing a service to the country” by remaining in office. “If he left, then Trump could appoint someone who would fire Mueller,” he said.