Justice Department Inspector General Michael Horowitz has been scheduled to testify before the Senate Judiciary Committee on Dec. 11, all but confirming the imminent release of his widely anticipated report into potential FBI and DOJ surveillance abuses against the Trump campaign.

A source told Fox News last month that Horowitz's upcoming report will shed light on why Connecticut U.S. Attorney John Durham's ongoing probe into potential FBI and Justice Department misconduct has transitioned into a full-fledged criminal investigation.

In announcing Horowitz's upcoming testimony, Judiciary Committee Chairman Lindsey Graham, R-S.C., called the independent watchdog a "good man" who has "served our nation well." Horowitz was appointed to the post by then-President Obama.

“I appreciate all the hard work by Mr. Horowitz and his team regarding the Carter Page FISA warrant application and the counterintelligence investigation of the Trump campaign," Graham said in a statement.

Page is the Trump campaign adviser whom the FBI targeted for surveillance beginning in 2016. The bureau, in its 2016 Foreign Intelligence Surveillance Act (FISA) application to monitor Page, flatly called him "an agent of a foreign power." Additionally, the FBI assured the FISA court on numerous occasions that other sources independently corroborated the dossier's claims but did not clearly state that the dossier's author worked for a firm hired by Hillary Clinton's campaign.

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Page was not charged with any wrongdoing despite over a year of federal surveillance, and he has since sued numerous entities -- including the Democratic National Committee (DNC) -- for defamation related to claims he worked with Russia. Meanwhile, the dossier that the FBI cited in its FISA application has largely been discredited as a political document rife with inaccuracies.

And, documents obtained by Fox News have suggested that internal clashes erupted in real time between the FBI and DOJ, concerning the strength of the bureau's case.

For example, just nine days before the FBI applied for its FISA warrant to monitor Page, FBI officials were battling with a senior Justice Department official who had "continued concerns" about the "possible bias" of a source pivotal to the application, according to internal text messages published by Fox News earlier this year.

The 2016 messages, sent between former FBI lawyer Lisa Page and then-Deputy Director Andrew McCabe, also revealed that bureau brass circulated at least two anti-Trump blog articles, including a Lawfare blog post sent shortly after Election Day that called Trump possibly "among the major threats to the security of the country."

Horowitz, in an initial report last year, flagged numerous senior FBI officials for tainting their work with the overt appearance of bias and leaking wantonly to the media, among other concerns. At the time, the watchdog said a more comprehensive review would be forthcoming.

“Mr. Horowitz will be appearing before the Senate Judiciary Committee on December 11, where he will deliver a detailed report of what he found regarding his investigation, along with recommendations as to how to make our judicial and investigative systems better," Graham continued in his letter.

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The FBI formally opened its counterintelligence probe into the Trump campaign July 31, 2016, several days after Page says he first met U.S. intelligence informant Stefan Halper at the symposium. From 2012 to 2018, the Defense Department paid Halper more than $1 million for consulting work.

"I had a longstanding relationship with Professor Halper," Page told Fox News this past June. "I always believe in 'innocent until proven guilty,' but my conversations with him intensified right in the month before my illegitimate FISA warrant in September 2016, when all these defamatory articles are being placed by the [Democratic National Committee]."

Page separately told Fox News in October that he was "frustrated" that Horowitz had not interviewed him directly.

Also in October, Horowitz told Senate and House lawmakers that the process of finalizing his report into potential FISA abuses was "nearing completion," according to a letter obtained by Fox News.

The "lengthy" draft report "concerns sensitive national security and law enforcement matters," Horowitz wrote in the letter, adding that he anticipated "the final report will be released publicly with few redactions."

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Horowitz noted that he did not anticipate a need to prepare or issue "separate classified and public versions of the report."

"After we receive the final classification markings from the Department and the FBI, we will then proceed with our usual process for preparing a final report, including ensuring that appropriate reviews occur for accuracy and comment purposes," Horowitz wrote in the letter. "Once begun, we do not anticipate the time for that review to be lengthy."