He was called the "Walrus," but Cambridge University professor Stefan Halper seemed remarkably agile and active in making contacts with Trump campaign officials in the summer and fall of 2016. Indeed, he not only actively consulted with at least three Trump campaign advisers but appears to have sought a position in the Trump administration.

Ordinarily that would not be notable. After all, Halper served in prior administrations, was a moderate Republican, and is a recognized academic who shared Donald Trump's hardline view of China. The problem is that Halper also may have been a paid informant for the FBI and CIA. Halper's role has triggered a justified referral by Deputy Attorney General Rod Rosenstein for investigation by the Justice Department inspector general. The allegations fall into a gray area of Justice Department guidelines which limit "overt" acts before an election but are ambiguous on covert acts like running the Walrus.

Three questions, however, stand out over his role. The details of Halper's work still are largely unknown. We know that the FBI carried out an investigation targeting Trump campaign officials with surveillance, document demands, and at least one informant. All of this was done through national security powers, where warrants are easily obtained and kept secret. We know this investigation began, at the latest, in July 2016 and that the Foreign Intelligence Surveillance Act application was based in part on a dossier paid for by the Clinton campaign.

We also know that key Justice Department officials expressed hostile views of Trump in emails, and that key Justice Department officials have been subjects of demotions and one criminal referral. Does this mean the use of Halper was improper or that the investigation was conducted in bad faith? No. Yet, there is a legitimate reason for an investigation into, as Rosenstein instructed, whether "anyone did infiltrate or surveil participants in a presidential campaign for inappropriate purposes," adding "we need to know about it and take appropriate action."

The allegations fall into the space between overt and covert acts for the purposes of Justice Department regulations. In 2012, a memo on "election year sensitivities" warned Justice Department offices about "the timing of charges or overt investigative steps near the time of a primary or general election." It warned that Justice Department officials "must be particularly sensitive to safeguarding the department's reputation for fairness, neutrality, and nonpartisanship."

The memo continued, "Simply put, politics must play no role in the decisions of federal investigators or prosecutors regarding any investigations or criminal charges. Law enforcement officers and prosecutors may never select the timing of investigative steps or criminal charges for the purpose of affecting any election, or for the purpose of giving an advantage or disadvantage to any candidate or political party."

Halper reportedly was part of a covert operation. However, Halper adds a new, potentially significant element to this controversy. Indeed, it is hard to understand the objections to the investigation of his role. All Americans should be concerned by the implications of an administration running a long investigation into the activities of its opposing party. Three questions could well determine if there was a serious problem of abusive tactics or merely bad optics in the running of the Walrus.

Timing

The date of Halper's work targeting Trump officials could prove key to the ongoing investigations in Washington. Former FBI Director James Comey has asserted that the probe into the Trump campaign did not start until the end of July 2016. However, news accounts continue to push Halper's work earlier and earlier in that month. Indeed, the Washington Post reported, "The professor's interactions with Trump advisers began a few weeks before the opening of the investigation, when (campaign foreign policy adviser Carter Page) met the professor at the British symposium."

If Halper's "interactions" began in June or earlier, there may be some debate when the investigation actually "opened." His work could not just contradict Comey's prior statements but raise new questions on why the FBI moved so quickly and intrusively against the Trump campaign.

Money

A lot of money is being tied to Halper, with some accounts as high as $2 million. Many of these reports seem dubious. The Pentagon Office of Net Assessment reportedly paid Halper more than $1 million for research and development in the social sciences and humanities. However, such money often goes to other experts for the creation of reports and the holding of events. We need to know what money was paid and its purpose.

Halper was an foreign relations expert and could have received money in that capacity, as opposed to being an informant or spy. Nevertheless, if he was paid hundreds of thousands of dollars as an informant, it would change how he is viewed. If he was paid as an asset, using him to target Trump figures reduces the nexus with the FBI dramatically. Other notable payments also exist, like his payment of $3,000 to George Papadopoulos, a Trump foreign policy adviser. Halper gave the money and travel compensation to Papadopoulos for a paper on energy issues.

However, when Papadopoulos met with Halper, Halper pressed him on whether he was involved in getting the Clinton emails and anything he knew about collusion. Papadopoulos was clearly viewed as a possible entry into the workings of the Trump campaign. If this money ultimately came from the FBI, it could constitute the use of federal funds to induce a Trump official to be an indirect or direct asset for the investigation.

Intrusion

Perhaps the most serious allegations deal with Halper's reported effort to advise the Trump campaign or secure a position in the new administration. If Halper was a longtime paid asset of the FBI and CIA, such a role would be deeply troubling. If successful, the FBI could have had a person working with the campaign or even in the administration who was on its covert budget. Even if they stopped paying Halper, it is doubtful that he would disclose his prior relationship. Trump officials have said they were unaware of the connection in their conversations with him.

In his meetings, Halper was clearly trying to influence or possibly join the campaign while working with the FBI. At a minimum, Halper met with with Trump campaign advisers, including Papadopoulos, Page and former national campaign co-chairman Sam Clovis. Trump economic adviser Peter Navarro reportedly submitted Halper's name for a post during the presidential transition. If the FBI knew Halper was actively seeking a role in either the campaign or the administration, this could be every bit as serious as Trump alleged.

While the media has tended to downplay these allegations, they are manifestly serious. The use of a paid FBI asset to target a national campaign in this way would be unprecedented. The closest we have come historically was the allegation in 1980 that aides to Ronald Reagan spied on Jimmy Carter's campaign and obtained confidential documents Carter used to prepare for a debate. While he has denied the allegations, one of those aides identified was Halper.

Jonathan Turley is the Shapiro Professor of Public Interest Law at George Washington University. You can follow him on Twitter @JonathanTurley.