Billionaire behind pardon effort pledged massive donation to Trump: Sources

New details about the Justice Department investigation into a possible scheme to lobby the Trump administration for a presidential pardon indicate that a now-deceased California real estate mogul donated $6 million to support President Trump -- and promised more.

California billionaire Sanford Diller gave the seven-figure sum, and pledged the potential for an even larger donation, as he pursued a pardon for his friend, a Berkeley psychologist in prison for tax evasion, according to documents reviewed by ABC News.

Diller at one point suggested he had the potential to become a donor on the scale of Sheldon Adelson, a Las Vegas casino magnate who has given hundreds of millions of dollars to Republican political causes, sources told ABC News and documents confirmed.

Donations from Diller do not appear on Trump's federal campaign reports. Sources familiar with the matter told ABC News that the $6 million in contributions were made in 2016 to a pro-Trump nonprofit political committee, which -- unlike a campaign -- is not required by federal law to disclose its donors or donation amounts.

It is routine for presidential candidates and other politicians to maintain political nonprofit entities to accept unlimited amounts of money from people who do not need to be identified, though there are some IRS restrictions on how the money can be used.

Diller had arranged for his friend, Berkeley psychologist Hugh Baras, to retain help from Abbe Lowell, one of the most prominent and powerful D.C. attorneys. Documents reviewed by ABC News indicate that Lowell prepared a memo to argue the case. But no pardon was ever issued and Baras, who was 73 at the time, served out his sentence.

"In efforts to seek reconsideration of a jail sentence or clemency, I was retained to learn the facts, research relevant laws, and write and submit to authorities a memorandum explaining why an elderly, unwell man who had never before had a run-in with the law ought not go to jail," Lowell wrote in an op-ed in the National Law Journal this week defending his efforts. "This is what I did. It is what attorneys do every day of every week."

Lowell most recently represented Jared Kushner and Ivanka Trump during the investigation into Russian meddling in the 2016 elections, and is not believed to be under investigation for his role in the matter, his attorney told ABC News.

Last week, Reid Weingarten, a friend and attorney for Lowell, said there was never any attempt to bribe the administration.

"Abbe came to believe there were legitimate arguments to be made that this guy shouldn't do time. Seeking clemency is a completely normal route," Weingarten said. "The fact that he pursued that -- there's nothing wrong with it."

Diller died in 2018 and Baras was released from prison in 2019. Baras did not respond to a request for comment from ABC News.

According to court documents unsealed for the first time last week, the government in August sought a court order "so that the investigative team [could] access" certain communications, and confront individuals in the case in order to take "investigative steps needed to complete its investigation."

"No government official was or is currently a subject or target of the investigation disclosed in this filing," a DOJ official said in a statement to ABC News last week.