The Republican chairman of the Senate Judiciary Committee revealed new details about his investigation of alleged Foreign Intelligence Surveillance Act abuses, detailing his plan to interview the FBI agents and Justice Department lawyers who questioned British ex-spy Christopher Steele’s sources.

Sen. Lindsey Graham of South Carolina spoke with Sharyl Attkisson on Full Measure on Sunday, providing the first detailed update in weeks about his progress in interviewing a couple dozen key current and former DOJ and FBI officials, including FBI Director James Comey and FBI Deputy Director Andrew McCabe, tied to the Trump-Russia investigation and flawed, secretive surveillance of onetime Trump campaign foreign policy adviser Carter Page.

“So the thing that intrigues me the most is that in January 2017, the primary sub-source, a Russian, who prepared all of the information to go to Christopher Steele to go in the dossier, was interviewed by the FBI and the Department of Justice,” Graham said. “There were four people in the interview, and he basically told them, according to the Horowitz report, ’This is bar talk. It isn’t reliable. I never meant it to be used this way. I can’t believe you’re getting a warrant based on this document.’ The odds that these four people dealing with the most high-profile investigation maybe in the history of the FBI did not tell Comey, McCabe, and people higher up, I think are pretty low. But that’s yet to be established.”

DOJ Inspector General Michael Horowitz conducted an investigation into allegations of FISA abuses and interviewed Steele. His report, released in December, identified at least 17 “ significant errors or omissions” in the Justice Department's and the FBI’s use of Steele’s dossier when pursuing FISA warrants to wiretap Page in 2016 and 2017.

The DOJ watchdog also criticized investigators for not informing the FISA court of exculpatory information obtained by the confidential human sources it deployed against Trump’s campaign. Following the release of Horowitz’s report, the Justice Department told the FISA court it believed the final two Page FISA warrants were “not valid,” and the FBI has moved to “sequester” all of the information gleaned from the Page surveillance.

Horowitz’s report revealed that the FBI interviewed Steele's primary Moscow-based sub-source multiple times beginning in January 2017, who “raised significant questions about the reliability of the Steele election reporting.”

Steele’s dossier claimed there was “a well-developed conspiracy of cooperation” between the Trump campaign and the Russians, which was “managed” by Trump campaign manager Paul Manafort by “using ... Page and others as intermediaries” with the Russians. The compilation of reports also asserted that in the summer of 2016, Page held “secret meetings” with Rosneft chairman Igor Sechin and Putin’s deputy chief Igor Divyekin. Page has denied all of this.

Horowitz’s report noted that “the Primary Sub-source made statements during his/her January 2017 FBI interview that were inconsistent with multiple sections of the Steele reports, including some that were relied upon in the FISA applications.” Horowitz said, “regarding the allegations attributed to Person 1, the Primary Sub-source's account of these communications ... contradicted the allegations of a ‘well-developed conspiracy’ in” Steele’s dossier.

“The renewal applications omitted the fact that Steele's Primary Sub-source, who the FBI found credible, had made statements in January 2017 raising significant questions about the reliability of allegations included in the FISA applications, including, for example, that he/she did not recall any discussion with Person 1 concerning Wikileaks and there was ‘nothing bad’ about the communications between the Kremlin and the Trump team, and that he/she did not report to Steele in July 2016 that Page had met with Sechin,” Horowitz wrote.

Steele was hired by opposition research firm Fusion GPS, which was funded by Hillary Clinton's presidential campaign and the Democratic National Committee through the Perkins Coie law firm.

The DOJ watchdog said the FBI conducted interviews of the primary sub-source in January, March, and May 2017 “that raised significant questions about the reliability of the Steele election reporting” and that the FBI interview in January 2017 “raised doubts about the reliability of Steele's descriptions of information in his election reports.” Horowitz’s report said that meeting was attended by "Case Agent 1," revealed to be FBI agent Stephen Somma, as a supervisory intelligence analyst and representatives of DOJ’s National Security Division. At that meeting, “the Primary Sub-source ... made statements indicating that Steele misstated or exaggerated the Primary Sub-source's statements.”

“Well, I can’t name them on television. They are people that I will be interviewing. Two worked for the Department of Justice. Two worked for the FBI,” Graham said of the upcoming witnesses. “McCabe and Comey are basically saying, ‘I didn’t know about all this.’ I find that hard to believe, so I’m going to go start at the bottom and work my way to the top, and I’ll let you know what we find.”

The primary sub-source called the infamous “pee tape” claims about Trump and prostitutes at Moscow’s Ritz Carlton nothing but “rumor and speculation” and disputed Steele’s claim that the story was “confirmed” by anyone, according to the DOJ watchdog report. The primary sub-source also disputed Steele’s claims about Page meeting with Sechin, and the supervisory intelligence analyst acknowledged that “the FBI was not able to prove or disprove Page's meeting with Sechin.”

Horowitz found “no evidence that the Crossfire Hurricane team ever considered whether any of the inconsistencies warranted reconsideration of the FBI's previous assessment of the reliability of the Steele election reports” or any indication that either DOJ’s Office of Intelligence or the FISA court were warned of these flaws during subsequent renewals.

Graham said he would interview certain unnamed DOJ and FBI officials in Horowitz’s report first, followed by public hearings including those who signed off on the Page FISAs: Comey, McCabe, former Deputy Attorney General Sally Yates, and former Deputy Attorney General Rod Rosenstein. He also plans to call current FBI Director Christopher Wray, who took over the bureau after Comey was fired in 2017.