The Justice Department's internal watchdog is set to release a highly anticipated report Monday that is expected to document misconduct -- including the deliberate falsification of at least one key document -- during the investigation into President Trump's 2016 campaign.

At the same time, the report, as described by people familiar with its findings, is expected to conclude there was an adequate basis for opening one of the most politically sensitive investigations in FBI history. It began in secret during Trump’s 2016 presidential run before then-Special Counsel Robert Mueller ultimately took it over.

The report comes as Trump faces an impeachment inquiry in Congress centered on his efforts to press Ukraine to investigate a political rival, Democrat Joe Biden — a probe the president also claimed has been politically biased. The House Judiciary Committee is expected hold a hearing Monday on the inquiry's findings.

The release of Inspector General Michael E. Horowitz's review is unlikely to quell the partisan battles that have surrounded the Russia investigation for years. It's also not the last word: A separate internal investigation continues, overseen by Attorney General Bill Barr and led by U.S. Attorney John Durham. That investigation is criminal in nature, and Republicans may look to it to uncover wrongdoing that the inspector general wasn’t examining.

Sources told Fox News in October that Durham's probe into potential FBI and Justice Department misconduct in the run-up to the 2016 election through the spring of 2017 has transitioned into a full-fledged criminal investigation -- and Horowitz's report will shed light on why Durham has been leading a criminal inquiry.

Horowitz has forwarded to Durham evidence that an FBI lawyer manipulated a key investigative document related to the FBI's secretive surveillance of former Trump adviser Carter Page in 2016 and 2017 -- enough to change the substantive meaning of the document, according to multiple reports last month.

"I think we'll learn part of the story tomorrow," Page told the Fox Business Network's Maria Bartiromo on "Sunday Morning Futures." "What I've learned from some of the leakers and one of the papers of record: a top reporter there said there's a lot of exculpatory evidence that's remaining classified, and there's been internal battles."

It is unclear how Barr, a strong defender of Trump, will respond to Horowitz's findings. He has told Congress that he believed "spying" on the Trump campaign did occur and has raised public questions about whether the counterintelligence investigation was done correctly.

The inspector general's investigation began in early 2018, and has focused in part on the FBI's surveillance of Page. The FBI applied in the fall of 2016 for a warrant from the secretive Foreign Intelligence Surveillance Court to monitor Page's communications, flatly telling the court that Page was an "agent" of a foreign power.

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Page was never charged and has denied any wrongdoing. The ultimately successful warrant application on Page relied in part on information from British ex-spy Christopher Steele – whose anti-Trump views have been well-documented – and cited Page's suspected Russia ties.

In its warrant application, the FBI inaccurately assured the Foreign Intelligence Surveillance Act (FISA) court on numerous occasions that media sources independently corroborated Steele's claims, and did not clearly state that Steele worked for a firm hired by Hillary Clinton's campaign and the Democratic National Committee (DNC).

Much of the Steele dossier has been proven discredited or unsubstantiated, including the dossier's claims that the Trump campaign was paying hackers in the United States out of a nonexistent Russian consulate in Miami, and that former Trump attorney Michael Cohen traveled to Prague to conspire with Russians. Mueller also was unable to substantiate the dossier's claims that Page had received a large payment relating to the sale of a share of Rosneft, a Russian oil giant, or that a lurid blackmail tape involving the president existed.

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Sen. Lindsey Graham, the chairman of the Senate Judiciary Committee, which is scheduled to hear testimony from Horowitz on Wednesday, said he expected the report would be "damning" about the process of obtaining the warrant.

"I'm looking for evidence of whether or not they manipulated the facts to get the warrant," Graham, R-S.C., told "Sunday Morning Futures."

Fox News' Brooke Singman, Fox Business Network's Maria Bartiromo and The Associated Press contributed to this report.