Who exactly is Joseph Mifsud, and what prompted his approach to George Papadopoulos in early 2016? The centrality of Mifsud to “Russiagate” and the mysterious lack of follow-up in Robert Mueller’s investigation remains the key unanswered question of the scandal, Eric Felten argues at RealClearInvestigations today.

Before we go there, let’s recall this exchange in the Mueller hearings in which Rep. Jim Jordan made the investigation’s strange pass on Mifsud a major story. Mueller’s team indicted Russian intelligence operatives for their interference operations and several Trump-world figures for lying to investigators, but Mifsud had done both — and never got named in any indictment. Jordan tried to get an answer from Mueller as to why, but Mueller refused to say:

Felten explains why this has become a big issue with Republicans, who are skeptical that the Mueller team investigated the full scope of Russian interference:

It was Mifsud, the report alleges, who took a trip to Moscow, and on his return “told Papadopoulos that the Russian government had ‘dirt’ on Hillary Clinton in the form of thousands of emails.”

Not so, said Mifsud in February 2017 when FBI agents interviewed him in the lobby of a Washington hotel. As Mueller recounted it in his report, Mifsud “denied that he had advance knowledge that Russia was in possession of emails damaging to candidate Clinton, stating that he and Papadopoulos had discussed cybersecurity and hacking as a larger issue and that Papadopoulos must have misunderstood their conversation.” The special counsel blamed Papadopoulos’ dissembling for disabling the FBI agents’ ability to get the goods on Mifsud: “The false information and omissions in Papadopoulos’s January 2017 interview undermined investigators’ ability to challenge Mifsud when he made these inaccurate statements.”

Maybe Mifsud was telling the truth. After all, the evidence to the contrary is supplied by someone who has done (a very little) time in jail for telling federal officials falsehoods. Which would at least explain why the special counsel did so little to pursue the professor. Having wrung a confession out of Papadopoulos for false statements about Mifsud, the special counsel’s team may have anticipated the difficulty they would face basing accusations against Mifsud on Papadopoulos’ say-so.

But it is another hypothesis altogether that is gaining traction with Republican lawmakers: the notion that the professor was indeed an intelligence asset, just not for Russia. “Joseph Mifsud is the key figure in the FBI’s opening of the official investigation of the Trump campaign, yet no one knows who he was working for,” Devin Nunes tells RealClearInvestigations.

Even though Mifsud is portrayed as the original contact between Russia and the Trump campaign, and key to the alleged reason the FBI took the rare and controversial step of opening a counterintelligence probe against a presidential campaign, Nunes says the FBI and the special counsel were strangely blasé about the professor. “Mifsud has contacts throughout western governments, none of whom seem concerned that they’ve been compromised by a Russian agent.”

Part of Nunes’ rationale for speculating that Mifsud was an American intel asset was because of his links to Western institutions. It seems more likely that such connections would make Mifsud more valuable to Moscow rather than the CIA. It’s also possible that Mifsud worked both sides of the street, or neither at all. However, if Mifsud was indeed a US intel asset, then Congress will need to find out who ordered him to bait Papadopoulos, and why. That’s why Republicans want to know about Mifsud, because it might point back to a political-hit operation that would make Watergate pale in comparison.

At the moment, the prospects for getting an answer to the question seem poor. Michael Horowitz’ inspector-general investigation into the beginnings of Operation Crossfire Hurricane will get released soon, perhaps in September, but Horowitz’ scope is the Department of Justice. The CIA would be beyond his purview, which means he’d only be able to determine what the FBI knew about Mifsud, if much of anything.

Appointing John Ratcliffe as director of national intelligence might uncork more, but if there is more, why isn’t CIA director Gina Haspel providing it? Mifsud’s name and picture are all over the place, so it’s not as if he can operate as an active asset now, if indeed he ever was one in the first place. As president, Trump can choose to declassify anything he likes (although with some potential for drastic consequences). Jim Jordan shouldn’t have to be berating Mueller about Mifsud; if there’s something besides smoke there, Trump and his team can provide it.

The best guess for why Mifsud hasn’t been fully explained is because he’s just not fully explainable. The lack of charges against him should be explained, however, because it certainly leaves the impression that the special counsel was playing favorites with obstructors.