As Special Counsel John Durham carries on with the investigation into the origins of the Russia investigation, widening his prosecutorial team, critical questions linger over the role played by FBI informant Stefan Halper and his longtime FBI handler, Stephen Somma.

Halper emerged in the middle of the firestorm in May 2018, when his identity as the secret FBI informant embroiled in Crossfire Hurricane was exposed. It cast a dark shadow on his prestigious career as a foreign policy expert, Cambridge professor, author and analyst with deep ties to intelligence figureheads and sources spawning the globe.

But since then he appears to have been hidden from public view. The whereabouts of Somma, who subsequently was exposed as his handler and shared blame for Foreign Intelligence Surveillance Act (FISA) mishaps against Trump campaign aide Carter Page, also have been unclear.

Despite both Halper and Somma being poised as having played a pivotal part in the U.S. counterintelligence operation Crossfire Hurricane – which officially ran from July 31, 2016, to May 17, 2017, to determine "whether individuals associated with Donald Trump's presidential campaign were coordinating, wittingly or unwittingly, with the Russian government's efforts to interfere in the 2016 U.S. presidential election" – neither of them have testified publicly about their roles and what they knew.

"The key is getting Halper (and Somma) to testify publicly, once he speaks, this whole thing unravels," Steven Schrage, a former senior G8 and congressional chief of staff, whose studies Halper directly supervised as the "Russiagate" scandal was playing out, told Fox News. "So, who is protecting him and why?"

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Trumpeted efforts to bring Halper into the limelight in recent months also have fallen into the abyss. 

An alumnus of three Republican administrations and given further gravitas by his esteemed position as a Cambridge University professor, Halper convened conferences and gatherings rich with high-profile guests including Michael Flynn, who served as Defense Intelligence Agency chief at the time, before his brief stint at Trump's national security adviser ahead of the Russiagate implosion. 

In June, Senate Judiciary Committee authorized Chairman Lindsey Graham, R-S.C., to issue subpoenas related to oversight of the FISA process and the Crossfire Hurricane investigation, on which Somma was named. 

"I want to know why all these counterintelligence investigations were opened to begin with," Graham said in a statement at the time. "This Committee is not going to sit on the sidelines and simply move on." 

Schrage had been working with Durham's investigation since 2019. However, he told Durham in June that he needed to reach out to other investigators due to their lack of action and concern that important evidence would stay hidden from the public past the 2020 election.

Days later, in a letter obtained exclusively by Fox News, dated June 8, 2020, Schrage informed Graham that he had "information that may be indispensable to revealing critical facts on the Crossfire Hurricane investigation."

"Your subpoenas and hearing may be the last chance to expose vital information being kept from you and that risks being buried after the 2020 election," Schrage, a former Senate chief of staff, wrote, adding that he was willing to meet with Graham or with his top staff members on short notice.  

After following up for several days, Schrage said he received a response from a staffer who said neither Graham nor his top aides were willing to meet on this evidence. However, a Senate Judiciary staffer told Fox News that the panel did not receive enough information to evaluate what the evidence was and that Schrage did not want to talk to a senior investigator in advance, which they had offered.

Then, the Senate Homeland Security Committee in September also voted in favor of authorizing depositions and subpoenas for 40 other people connected to the Russia-Trump quagmire – including both Halper and Somma. In early October, the committee subpoenaed Halper as part of its investigation, for records about his work during the Trump-Russia inquest. The committee has been chaired by Sen. Ron Johnson, R-Wis.

"You are hereby commanded to appear before the Committee on Homeland Security and Governmental Affairs of the Senate on October 14, 2020, at 5:00 p.m. at its committee room," the subpoena read, adding that there, he was compelled to "produce all records related to the Federal Bureau of Investigation's Crossfire Hurricane investigation."

But Halper, now 76, failed to show, and it's uncertain whether the matter will be pushed further. According to a source connected to Durham's inquiry, who spoke on the condition of anonymity, Halper allegedly claimed to be sick for much of the past year.

Yet, the unanswered questions have remained flagrant.  

Halper was Schrage's Ph.D. supervisor throughout his studies, starting from 2013. While Halper technically remained his adviser until he received his doctorate in 2019, they did not speak after Halper's outed in 2018. Schrage also was the official who first connected Halper with Page at a security conference in July 2016.

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Former M16 agent Christopher Steele produced a new report for the Clinton campaign a week later, the first one targeting Page. Crossfire Hurricane formally opened 11 days later. From Schrage's lens, it remained strange that the three people he considered to be at the center of the investigation – Halper, Somma and Steele – have been protected from issuing public statements or congressional testimony. 

It still was not evident how long Halper – who then remained in communication with Page until at least July 2017 – worked as an FBI informant in the Russia-Trump team inquest. The last in-person meeting he had with Halper, Schrage said, was in the spring of 2018, shortly before his identity in the probe was leaked. 

Page has long alleged that he specifically told Halper he never met with two former Russian officials mentioned in the largely discredited Steele dossier.

A Department of Justice (DOJ) inspector general's report into FISA abuses, released last December, blamed Somma – a New York field office-based FBI counterintelligence investigator – for being "primarily responsible for some of the most significant errors and omissions" of the 17 found in the FISA warrant application against Page. 

The DOJ affirmed that the court should not have approved the FISA warrant for Page. To date, Durham's investigation has brought about just one criminal charge; former FBI lawyer Kevin Clinesmith pleaded guilty this past August to altering an email related to Page's surveillance. That prosecution, though, did not allege a more widespread conspiracy within the FBI. 

Yet, why and how Halper has managed to evade law enforcement or publicly take the stand also called into question the status of Somma, dubbed "Case Agent 1."

From Schrage's lens, it all came down to Halper and Somma in piecing together the missing pieces of the original puzzle. 

FBI documents compiled in late August 2016 ultimately showed that there was inadequate documentation to support a FISA application on Page. Yet, the matter was pursued by Somma amid a "pattern of (intentional) errors."

"We also did not find his explanations for so many significant and repeated failures to be satisfactory," the IG report, led by Michael Horowitz, stated, acknowledging that there was not enough information to ascertain "whether it was sheer gross incompetence that led to this versus intentional misconduct or anything in between."

Horowitz's findings concluded that Somma excluded critical information provided by Halper – who was termed "Source 2" – which included Page denying to Halper that he had ever met with the Russian figures in the Steele report. 

A Senate Judiciary staffer told Fox News that sufficient information – given the limited time frame – has been extracted on Halper from the documents and raw transcripts made available. The source declined to comment on specifics in terms of who was interviewed, including Somma, but said the FBI has provided access to all requested subjects throughout the investigation. However, this has been limited only to those who remained employed at the bureau.

Representatives for the Senate Finance Committee Chairman Chuck Grassley, as well as the Office of the Director of National Intelligence (ODNI), referred the Halper subpoena query to the Homeland Security Committee. 

The Senate Homeland Security Committee did not respond to requests for further comment. The FBI declined further comment on the subpoena matter, reiterating its previous statement that, "under Director [Christopher] Wray's leadership, the FBI has been, and will continue to be, fully cooperative with Mr. Durham's review. This includes providing documents and assigning personnel to assist his team."

Halper also has been staying quiet. 

"Neither I nor Professor Halper will agree to an interview and will not comment further on matters relating to Sen. Johnson's inquiries," Robert Luskin, an attorney for Halper, told Fox News in an email. 

"It is not even clear if he did an interview with Mueller, there is a massive hole left here that needs to be filled," Schrage said.

It also remained murky whether Halper was paid to communicate with Trump campaign figures – using U.S. taxpayer dollars. Public records from the Pentagon's Office of Net Assessment (ONA) showed that Halper received $282,000 in 2016 and $129,000 in 2017.

Weeks after at least one large payment was made, the wiretapping of Page started. Schrage has noted that Halper was profusely thankful for the introduction to the Trump campaign confidante, which he "never really understood," and that he exhibited "odd" behavior at the time. 

A January-dated letter authored by Grassley to James Baker, director of the ONA, underscored that a request for "all records related to Professor [Stefan] Halper's contracts with DoD" six months earlier had not been met. When Grassley raised the "failure to comply" a month later, further documents were issued, but he claimed in the letter that the "production of documents still did not include all records requested."

"For example, you failed to provide all Halper-related documents that you delivered to the Department of Defense Office of Inspector General (DoD IG) for their review," he wrote, additionally highlighting other questionable payments to Halper for an array of unclear DOD contracts and "unknown" foreign entities.

However, Halper and Somma were not the only critical figures within Russiagate who have been shielded from public view.

Joseph Mifsud, a Maltese professor working at the security and intelligence-focused Link University in Rome – who in 2016 told fellow Trump campaign aide George Papadopoulos that the Russians "had dirt" that could damage Hillary Clinton's presidential campaign before the opening of Crossfire Hurricane – has not been seen publicly since his name was exposed in the fall of 2017.  

Former FBI Director James Comey implied in May of last year that Mifsud was something of a "Russian agent." Yet the Mueller team never indicted him, despite statements in the report that he lied three times to investigators. It has long been fodder for debate as to whether Mifsud was also on the payroll of a Western foreign intelligence agency – public or private. Rep. Devin Nunes, R-Calif., who was chairman of the House Intelligence Committee from 2015 to 2019, said emphatically at the time that Mifsud was not an agent at the behest of Moscow. 

But, when questioned by Republican lawmakers in a House Judiciary Committee hearing in June as to why Mifsud was not charged with the crime of giving false statements despite other indictments for fewer offenses, Mueller responded: "Well, I can't get into it and it's obvious, I think, that we can't get into charging decisions."

An attorney for Mifsud, who has not had direct contact with him since his dispersal from public view, told Fox News that he remained in some form of hiding in November. Meanwhile, and despite his crucial role, Halper's name did not appear in the 2019 unveiled Mueller report

This Nov. 12, 2014 photo made available by the Organization of American States shows Maltese academic Joseph Mifsud during a meeting in Washington. (Juan Manuel Herrera/OAS via AP, File)

During his televised congressional testimony, Mueller also was questioned about why he never interviewed Schrage – the connector between Halper and Page – or others who would might reveal improprieties in how the investigation began. Mueller again declined to answer.

Nonetheless, it's unclear when – or if – Durham will issue a report on his findings.

The special counsel, however, under the scope order of Attorney General William Barr, "is authorized to investigate whether any federal official, employee, or any other person or entity violated the law in connection with the intelligence, counterintelligence, or law-enforcement activities directed at the 2016 presidential campaigns, individuals associated with those campaigns, and individuals associated with the administration of President Donald J. Trump, including but not limited to Crossfire Hurricane and the investigation of Special Counsel Robert S. Mueller, III."

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As it stands, the Judiciary Committee has been in the process of evaluating whether it will draw conclusions before the end of the term, pass the information onto the incoming chairman or do a combination of both – but the steps going forward rest heavily on the results of the Georgia runoff elections in early January.

“If the Democrats win Georgia,” another staffer said, “then this is probably just going to go away.”