Shortly after Michael Flynn was forced out of the Trump administration, his lawyer pushed out a statement claiming that the ousted national security adviser had “a story to tell.” One top Democratic senator investigating Russia’s election interference thinks he’s already telling it.

Sen. Sheldon Whitehouse (D-RI), a former U.S. attorney and ranking Democrat on the Senate Judiciary subcommittee on crime and terrorism, says the “tea leaves” suggest Flynn is cooperating with the special counsel’s Russia’s probe. He laid out the “signals” in a pair of interviews on CNN and MSNBC this week.

For one, Whitehouse said, Flynn has gone radio silent. He is not speaking with the press and, after requesting immunity in exchange for interviews with congressional committees in March, has refused to testify publicly. Then there’s the rash of subpoenas out of the Eastern District of Virginia for bank records and documents relating to the retired lieutenant general’s consulting firm, Flynn Intel Group. In Whitehouse’s words, the FBI also has Flynn “dead to rights” on a statement he gave to the FBI in late January about his contacts with the Russian ambassador to the United States, Sergei Kislyak. Current and former U.S. officials told the press that he denied discussing sanctions against Russia in that interview with bureau agents—an omission that could have grave consequences.

Whitehouse also noted that Comey testified before his committee that it was “long-standing practice” for cooperating witnesses to clear up any outstanding compliance issues with the federal government. Flynn retroactively registered as a foreign agent in March for lobbying work he did on behalf of Turkey shortly after leaving the Trump administration, as Whitehouse pointed out.

There is no proof or public indication that Flynn is cooperating with the special counsel. His lawyer, Robert Kelner, did not respond to TPM’s request for comment on Tuesday. Flynn has not been charged with a crime, and Kelner has previously denounced what he called “unfounded allegations, outrageous claims of treason, and vicious innuendo” against Flynn.

Experts on national security law who spoke with TPM said Whitehouse’s “signals” alone are not enough of a basis to assume Flynn’s cooperation.

“There are a lot of reasons he could be going silent, including being smart and having counsel tell him to do so because of his exposure,” Rebecca Lonergan, a former federal prosecutor who handled foreign surveillance cases, told TPM, acknowledging that Whitehouse may possess information that the public does not.

“[Whitehouse] is likely basing this off his understanding of how these investigations unfold and the fact we knew four months ago that Mike Flynn wanted and was willing to speak,” Juliette Kayyem, a national security analyst who first raised suspicions that Flynn may be cooperating with federal investigators back in March, told TPM.

As Kayyem noted at the time, other Trump allies known to have contacts with Russia, including former campaign adviser Carter Page and the President’s son-in-law and adviser Jared Kushner, have agreed to come before congressional committees investigating Russia, but Flynn has not.

There are plenty of reasons why both Flynn and the special counsel would be interested in some sort of cooperation agreement, legal experts told TPM.

“It’s a no-risk proposition for the government to flip someone like Flynn,” Lonergan said.

As a member of the Trump campaign, transition, and administration, Flynn may have information about other Trump associates of interest to prosecutors. Meanwhile, he is the subject of a federal criminal probe and likely eager to reduce any possible charges.

“In most of these complex criminal investigations, deals are offered,” Kayyem told TPM. “And if you thought about who is the most vulnerable link, it’s clearly Mike Flynn.”

Flynn is reportedly under scrutiny for a host of issues ranging from his failure to disclose payments from Russian firms, his lobbying work on behalf of the Turkish government during the campaign, the content of his contacts with Kislyak, and whether he knowingly lied to the FBI about them.

Several of those issues touch on other members of Trump’s inner circle, making him a potential gold mine of information for investigators. Flynn was reportedly present at a December meeting in which Kushner spoke to Kislyak about establishing a secret communications backchannel between the Trump transition team and the Kremlin. He also reportedly falsely told Vice President Mike Pence that he did not discuss sanctions during a separate conversation he had with Kislyak during the transition.

Investigators will want to know “who he met with, who knew about it, who advised him to do it, was it an order or an instruction,” said Jon Michaels, a national security law expert at University of California Los Angeles Law School. “Did you kind of go off on your own without their knowledge or direction? What kind of feedback did you relay back to the administration-elect?”

As Phillip Bobbitt, director for the Center for National Security at Columbia University Law School, points out, Flynn “could be the one person” who could implicate Trump and Pence in the Russia investigation.

Bobbitt posited in a May blog post for LawFare that Trump ordered Flynn to talk to Kislyak about lifting sanctions. This directive, Bobbitt says, would explain why the administration kept Flynn on staff for 17 days after the Justice Department warned that he was “compromised with regards to the Russians.”

“If Flynn were to be a prosecution’s witness, he would be able to say whether or not he did in fact lie to the Vice President,” Bobbitt told TPM, or if he was “told to say he lied to the Vice President” as cover.

Bobbitt cautioned that we won’t really know if Flynn has flipped until a witness list comes out, but that given the torrent of leaks about this investigation, the public is likely to see that list soon after Flynn’s own attorney does.

“If Gen. Flynn turns up on it as a witness for the prosecution, that pretty much says it all,” Bobbitt said.