Republicans on the House intelligence committee investigating Russian interference in the 2016 election have refused Democratic entreaties to subpoena Twitter for direct messages of Donald Trump associates, multiple sources familiar with the matter tell The Daily Beast.

Sources would not share with The Daily Beast specifically whose DMs committee Democrats wanted to subpoena Twitter to acquire. But in hearing transcripts, Democrats have indicated they want DMs concerning Donald Trump Jr. and Trump consigliere Roger Stone—both of whom have been linked to WikiLeaks, which famously released hacked emails from the Democratic National Committee during the 2016 campaign.

It’s the latest sign that the Republicans on the hyper-factionalized committee are willing to focus on anything but potential collusion between Donald Trump and the Kremlin in the 2016 election. Trump’s associates tend to share their boss’ love for Twitter and, like many users of the social network, have been known to use direct messaging for sensitive communications.

And it comes as frustrated Democrats are accusing their Republican colleagues behind closed doors of intransigence that leaves them in a precarious position for any investigation: being asked to trust witnesses without the tools to verify their stories.

“For months, we have repeatedly requested that the Committee subpoena Twitter for communications between numerous persons of interest in our investigation,” Adam Schiff, the ranking Democrat on the committee, confirmed to The Daily Beast.

“A complete investigation would subpoena relevant communications records—including Twitter messages—to corroborate or contradict witness testimony,” added Eric Swalwell, a California Democrat on the committee and a former prosecutor.

“The GOP has been unwilling to do that. If we don’t do that, we are conducting a take-them-at-their-word investigation. There are too many Trump team members who are not worthy of being taken at their word.”

Democrats who want to subpoena Twitter for the private messages of Trumpworld figures are operating on the theory that the communications would either reveal substantive discussion of election machinations tied to Russia or vindicate the denials of actual and potential Trump-camp witnesses. But the Republicans have sat on the requests instead of fulfilling them or denying them outright.

Representatives for committee chairman Devin Nunes and Russia investigation chief Mike Conaway did not reply to a request for comment.

“ We are conducting a take-them-at-their-word investigation. There are too many Trump team members who are not worthy of being taken at their word. ” — Rep. Eric Swalwell

Democrats are getting restless. They’ve urged in committee hearings dominated by Nunes’ accusations of surveillance malfeasance that the Republicans are blocking access to witness documentation, including travel records and communications logs. The DMs fall in that category.

Twitter, for its part, has pledged to cooperate with both the House and Senate Russia inquiries and special counsel Robert Mueller’s unfolding inquiry. But the company has said a lot less about how it cooperates. Turning over a user’s DMs without being lawfully compelled to do so would spark serious questions about how the company treats user privacy with implications far beyond the Russia probe.

“Twitter continues to work with the Special Counsel’s Office and with Congress throughout their investigations, providing relevant information and cooperating through appropriate law enforcement channels,” the company said in a Friday statement.

There has been an exception to the committee’s inability to get DMs from relevant Twitter users: Donald Trump Jr.’s exchanges with WikiLeaks, which were published in part by The Atlantic in November. In the published DMs, WikiLeaks nudges the younger Trump toward its 2016 publication of Democratic emails that U.S. intelligence assesses Russia hacked, and even suggests that Trump refuse to concede the election if he lost. Congress acquired those messages not from Twitter, but from the younger Trump’s attorneys—raising questions about how complete the Trump Jr.-WikiLeaks colloquy actually is.

On Feb. 5, the committee met to consider the release of the Democratic rebuttal to Nunes’ accusations against the FBI and Justice Department. But the transcript revealed a deep Democratic frustration over the committee’s inability to access all sorts of relevant documentation (PDF).

For example: Peter King, a Long Island Republican, referenced not “see[ing] anything at all” to contradict the Trump attorney Michael Cohen’s insistence that Cohen never met in Prague in August 2016 with a Russian official.

Schiff, the senior Democrat on the panel, replied in the meeting: “What we have not had the opportunity to do is determine whether he was telling us the truth, because we have made requests to get documents, the subpoenaed documents, and the majority has been unwilling to support those requests to subpoena documents. When that is the case, then we have no way of verifying or disproving information.”

Among the information Schiff said the GOPers had declined steps to acquire are subpoena requests for unspecified Trump Jr. documents and unspecified Deutsche Bank records. (Trump is approximately $360 million in debt to Deutsche Bank, which faces accusations of acting as a vehicle for Russian money laundering, and there are disputed reports that Mueller has served subpoenas on the bank.)

“Numerous times, we have asked for documents, we have requested to subpoena documents from Twitter when we know there were direct communication between Don Jr. and Twitter, and Roger Stone and Twitter. These requests have gone nowhere with [the] majority,” the Feb. 5 meeting transcript records Schiff saying.

“ We have requested to subpoena documents from Twitter when we know there were direct communication between Don Jr. and Twitter, and Roger Stone and Twitter. These requests have gone nowhere. ” — Rep. Adam Schiff

It wasn’t just Don Jr. who was prone to DMing about the election. Stone, in August and September 2016, DM’d with the Russian cutout Guccifer2.0, an intermediary that claimed to provide the DNC material to WikiLeaks. Stone has also claimed to have a backchannel to WikiLeaks, which would explain his prescient fall 2016 predictions about material damaging to Democrats the group would publish. But it’s not clear if that backchannel, said to be radio host Randy Credico, is genuine, and WikiLeaks has denied it.

Nunes, the committee chairman, has wide-ranging authority for subpoenas under the committee bylaws (PDF). He hasn’t seen fit to subpoena Twitter for the DMs, but has subpoenaed Fusion GPS, the political research consultancy that sponsored ex-British spy Christopher Steele’s dossier. That followed on an August subpoena (PDF) to the FBI and Justice Department for documentation surrounding their “relationship” to Steele and the dossier. More recently, Nunes has announced unilateral plans to investigate Trump investigators and members of the Obama administration, either at the current Justice Department or the State Department under John Kerry.

“The committee’s rules provide that only the chairman can authorize a subpoena, and a serious investigation requires that the committee not simply take witnesses’ word at face value, but verify their testimony when possible through communication records obtained from third parties,” Schiff told The Daily Beast.

“And while that power has been used freely against government officials and Fusion GPS, for the purposes of the Russia investigation this vital investigative power has been foreclosed.”