The Justice Department watchdog is expected to criticize the FBI for leaving out potentially exculpatory evidence related to George Papadopoulos in a wiretap application targeting another former Trump campaign adviser.

In a draft of his forthcoming report, Inspector General Michael Horowitz said the Foreign Intelligence Surveillance Act applications related to the surveillance of Carter Page after he left the campaign should have included an August 2016 statement Papadopoulos made in London to Stefan Halper, a Cambridge professor who was working with the FBI as an undercover informant.

Sources told the New York Times this statement could be construed as exculpatory or self-serving. Papadopoulos claims in his book, Deep State Target, that he had no ties to Russia.

Some Republicans who have seen the relevant documents argued they were exculpatory. Former South Carolina Rep. Trey Gowdy said in May there were classified transcripts of recorded conversations between FBI informants and Papadopoulos that had "the potential to be a game changer.”

In July, Fox News reported the Justice Department was intent on reviewing transcripts of recordings that at least one government informant made of conversations with Papadopoulos, which happened as Attorney General William Barr and U.S. Attorney John Durham ramped up their investigation into the origins of the Russia investigation. That administrative review is now a criminal investigation.

Papadopoulos was swept up in Robert Mueller’s special counsel investigation under suspicion of trying to make inroads with the Russians. His interactions with the mysterious Maltese academic Joseph Mifsud allegedly led to the FBI opening a counterintelligence inquiry into the Trump campaign in July 2016, which predated Mueller's appointment. Papadopoulos pleaded guilty in October 2017 to making false statements to the FBI about his contacts with Mifsud and served just 12 days in federal prison late last year. He is now running for Congress.

Papadopoulos and other Trump allies have also claimed Mifsud was used by the FBI and the CIA to set up the Trump campaign.

In his report, slated for release on Dec. 9, Horowitz is expected to debunk the theory that Mifsud was working for Western intelligence. The inspector general also concluded, counter to theories favored in pro-Trump circles, that the FBI did not deploy undercover agents or informants to collect information on the Trump campaign itself and that the opening of the FBI's Crossfire Hurricane counterintelligence investigation was justified.

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Horowitz's findings bolster FBI Director Christopher Wray, who earlier this year disputed Barr's use of the word "spying" to describe the surveillance related to members of the 2016 Trump campaign and their suspected ties to Russia. During an interview with Fox News on Friday, Trump himself said he has heard Horowitz's report will be "historic" and surmised a "spying" plot against his campaign reached the "highest levels" of government.

The applications presented to the Foreign Intelligence Surveillance Court have been roundly criticized by Republicans, especially the FBI’s reliance on the dossier compiled by British ex-spy Christopher Steele, who was being paid by the Hillary Clinton campaign and the DNC through Fusion GPS via the Perkins Coie law firm. Republicans said the FBI did not verify the dossier before using it and that the bureau hid key facts from the court. Democrats defended the FBI’s actions.

Texas Rep. John Ratcliffe, who dropped out of consideration to be Trump's spy chief earlier this year, said documents "would expose certain folks at the Obama Justice Department and FBI and their actions and their actions taken to conceal material facts from the Foreign Intelligence Surveillance Court."

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Horowitz is expected to condemn the FBI for failing to inform the judges on the FISA Court of potential problems with the dossier.

Other leaks about the draft report show Horowitz found missteps and lapses in judgment but no evidence of political bias by top officials tainting the Russia investigation. Horowitz's investigators did find that an FBI lawyer, identified as Kevin Clinesmith, allegedly altered a document related to the surveillance of Page but determined Clinesmith's actions did not taint the overall validity of a renewal application.

The initial warrant application was approved in October 2016, and the final of three renewals came in June 2017.

Page, an American citizen who was suspected to be a Russian asset but was never charged, claimed he has not been given a chance to provide any input for Horowitz's "one-sided" report and filed a lawsuit with the U.S. District Court for D.C. last month accusing the Justice Department of Privacy Act violations and demanding an opportunity to review the FISA report before it is released to the public.

Horowitz's FISA report will follow a major audit released this month that found a slew of issues with the FBI's validation processes for secret sources and another that added the Justice Department's handling of government surveillance tools to a list of the agency's most "pressing concerns."