George Conway said "any fair jury" would convict Trump over his handling of classified documents.
While on "The New Abnormal" podcast, Conway also said a strong attorney couldn't do much for Trump.
"The one way he had out of this was to basically turn the documents over a year ago," Conway said.
Conservative lawyer George Conway in a recent interview said it would be difficult for "any fair jury" not to convict former President Donald Trump over his handling of classified and top secret materials after he left the White House.
During an episode of the Daily Beast's "The New Abnormal" featuring journalist Molly Jong-Fast, Conway said that he "can't guarantee" that the former president will be jailed, but stated that "there's a reasonable likelihood of it."
"I think it's going to be very difficult for the Justice Department to decline prosecuting him," Conway said. "I think before any fair jury, he'd have to be convicted based upon what we're seeing. There's still more evidence that needs to come out, but everything points to him being in a heap of trouble and we haven't seen everything that the Justice Department has."
When Jong-Fast asked what a "good lawyer" could do for Trump, Conway replied: "Nothing."
"The mistakes he made, he already made," Conway said. "The one way he had out of this was to basically turn the documents over a year ago, and not chuck the government around. They wouldn't have prosecuted him, even though if you or I - if we had taken this shit home - we would be in jail."
Last month, Trump's Mar-a-Lago residence in Florida was searched by the FBI, where federal officials retrieved several boxes of classified and top secret documents.
The subsequent release of the search revealed that agents were looking for documents connected to potential violations of the Espionage Act, which bars the unauthorized removal of defense-related information that could aid a foreign government. Trump is also being investigated for potential obstruction of justice violations.
The documents - regardless of whether or not they were considered to be classified - were supposed to be turned over to the National Archives upon the former president's departure from 1600 Pennsylvania Avenue, per the Presidential Records Act.
Conway said that an issue for the former president was his retention of classified documents despite the fact that one of his lawyers signed a statement to the Department of Justice informing them that all the records had been turned in.
"It's going to get interesting," Conway said on the podcast. "He makes everything worse because [Trump's lawyers are] doing what he wants them to do. He wants to go on the offense."
"The problem is he has no weapons to go on the offense with. And he has no legal arguments. He has no defense. He only has lies," he added.
Conway, who is married to former 2016 Trump presidential campaign manager and ex-White House counselor Kellyanne Conway, has in recent years attracted a large social media following and become a frequent presence on cable television for his sharp criticism of the former president - a huge contrast to his wife's longtime support of the ex-commander-in-chief.
Kellyanne Conway earlier this summer said on CNN that there has been "a lot of hurt" in her marriage connected to her husband's opposition to Trump, which she also described in her memoir, "Here's the Deal."