On Feb. 15, 2017 — that would be 16 months ago — Senate Judiciary Committee chairman Chuck Grassley, R-Iowa, and ranking Democrat Dianne Feinstein, D-Calif., asked the Justice Department to turn over the transcript of fired national security adviser Michael Flynn's infamous call with the Russian ambassador, plus other documents related to the Flynn case.

The department refused.

Some of Grassley's and Feinstein's questions were answered the next month, on March 15, 2017, when the FBI's then-director, James Comey, briefed the committee on Flynn and other matters in the Trump-Russia investigation. It was at that briefing that Comey told lawmakers the FBI agents who interviewed Flynn did not believe he lied to them.

"Then-director Comey led us to believe during that briefing ... that the Justice Department was unlikely to prosecute [Flynn] for false statements made in that interview," Grassley wrote later.

After the March 2017 briefing, Grassley and others made the reasonable assumption that Flynn would not be charged. They were surprised on Dec. 1, 2017, when — months after the Trump-Russia investigation passed from Comey and the Justice Department to special counsel Robert Mueller — Flynn pleaded guilty to lying to the FBI.

Last month, Grassley, this time without Feinstein, repeated his demand for the Flynn transcript, and also for the FBI's so-called 302 report, in which the agents who interviewed Flynn made extensive notes on what was said. Grassley also asked for any other notes or documents relating to the interview. And Grassley asked that the FBI make available agent Joe Pientka, one of the two agents (along with Peter Strzok) who conducted the Flynn interview.

Again, the Justice Department refused, and this time with more than a hint of impatience. In a May 29, 2018, letter to Grassley, assistant attorney general Stephen Boyd recounted details of the Flynn plea deal at length and delivered what boiled down to a simple message: Flynn pleaded guilty. You understand? He's guilty. Now stop bugging us.

"Whatever Mr. Comey may have said and whatever Mr. Flynn's demeanor," wrote Boyd to Grassley, "the evidence in the public record proves beyond any reasonable doubt that Mr. Flynn knowingly made false statements about contacts with the Russian ambassador." Referring to the Flynn case as a "pending criminal prosecution" — Flynn is currently awaiting sentencing — Boyd said turning over evidence to Congress could create "the reality or appearance of political interference."

If Boyd's letter was an attempt to mollify Grassley, it didn't work. And now, long after first requesting the documents, the chairman's patience appears to be running thin.

"The department's reply ... is insufficient," Grassley wrote in a June 6 response, adding that Boyd "relies on improper excuses in refusing to provide the requested information."

Grassley noted that he and the rest of the committee waited for more than a year for the Flynn criminal inquiry to conclude. "It has been more than five months since his guilty plea," Grassley wrote. "Thus, there is no longer any legitimate reason to withhold facts from the Senate about the circumstances of his conversations with the Russian ambassador and his FBI interview."

The chairman specifically did not buy the department's argument that Grassley might be interfering with a "pending criminal prosecution." "There is no pending prosecution" with the guilty plea five months in the past, Grassley argued.

"Simply disclosing facts to the committee could not possibly 'interfere' with the case at this late date," Grassley continued, "assuming those facts are consistent with the representations that prosecutors arranged for Lt. General Flynn to swear to in federal court."

That was the little bomb in Grassley's letter: The chairman raised the possibility that the facts of the case — the evidence in the phone conversation transcript and the FBI 302 — might somehow be at odds with the particulars of Flynn's plea. And in case anyone missed the reference, in the next sentence, Grassley wrote: "If the facts are inconsistent with the plea agreement, that would be an entirely different kettle of fish."

Grassley explained that his request was not done on Flynn's behalf, nor on the FBI's. "It might not be in the interests of either the defendant or the prosecutors to disclose facts inconsistent with the plea agreement," he wrote. "However, it would absolutely be in the interest of Congress and the American people to be aware of any such inconsistencies that may exist."

Grassley noted that the Flynn case has been talked and talked and talked about. There have been multiple leaks about it. Comey has talked about it during his book tour. A White House memo outlining the developments of January and February 2017 has been leaked. Given all that talk, Grassley wrote, "Presuming that the facts are consistent with the plea agreement, there is absolutely nothing for the department to hide and no reason to act like it has something to hide."

"Congress has a right to know the full story and to know it now."

It's likely Grassley will eventually get what he wants. After all, in August 2016, in the middle of the presidential campaign, the FBI gave Congress the 302s from interviews with Hillary Clinton and others in the email investigation — an investigation that would be re-opened a few months later. Congress also received 302s in investigations into the Waco debacle, the Oklahoma City bombing, and the Clinton pardon scandal, among many other examples.

But why does Grassley want the Flynn 302 so much? What is the source of the clear skepticism in his letter? What does he believe went wrong in the Flynn investigation?

First of all, Grassley is a fervent believer in congressional oversight. He is also a long-time supporter of inspectors general, who investigate their agencies and report to Congress. Above all, Grassley simply believes lawmakers have a right to know.

That certainly applies to the Flynn case. "In a briefing in March of 2017, then-FBI Director Comey indicated to Chairman Grassley and Ranking Member Feinstein that agents who interviewed Lt. Gen. Flynn saw no signs that he was being untruthful, and that the Department was unlikely to bring charges against him," said Judiciary Committee spokesman Taylor Foy in an email statement. "Obviously, that wasn't the case, and Mr. Comey has since denied that he ever suggested otherwise. The committee needs a better understanding of the FBI's interview with Mr. Flynn to reconcile these inconsistencies. Considering that a plea agreement was entered in this case months ago, there's no reason for the Department to continue withholding information related to the FBI's investigation into Mr. Flynn."

Beyond that — and this is referring to Congress generally, not Grassley specifically — there's no doubt that a number of Republicans suspect the Flynn case is not what it seems. They know that Flynn, a former head of the Defense Intelligence Agency, would have been keenly aware of U.S. surveillance capabilities and practices, and thus would have known that a conversation with the Russian ambassador was highly likely to be intercepted and recorded. They find it hard to believe that Flynn would have knowingly lied about a conversation when he knew his questioners had a transcript of the conversation.

They believe that Comey was telling Congress the truth when he said the Justice Department did not anticipate charging Flynn. And they know that something changed. That something, of course, was the arrival of Mueller. An investigation that appeared to be heading for no prosecution was revved back up and resulted in a false statements guilty plea.

Was that because some new and damning information was discovered? Was it because Mueller saw the case as a vehicle for pressuring Flynn to become a witness against the president? Was there some other reason?

The FBI 302 will not provide all the answers. But it will be a start.