Even after retaking the House last Tuesday, Democrats on Capitol Hill were nervous. “There are a lot of things that could happen between now and when we take the majority on January 3,” one Democratic congressional aide told me the following morning, as the election results were still coming in. “Most specifically, there is a lot that can happen in the Mueller space.” The warning was prescient. Within hours, Donald Trump announced the resignation of Attorney General Jeff Sessions, and named Sessions’s obsequious chief of staff, Matthew Whitaker, as the acting head of the Justice Department. As I reported last week, Washington insiders fear Trump could use Whitaker to obstruct the Russia investigation by narrowing its scope, choking off resources, or even refusing to release Robert Mueller’s final report.

Just as quickly as Trump moved to protect himself from Mueller, however, congressional Democrats are threatening to use Whitaker’s appointment as more evidence against the president. “If he doesn’t recuse himself, if he has any involvement whatsoever in this Russia probe, we are going to find out whether he made commitments to the president about the probe, whether he is serving as a back channel to the president or his lawyers about the probe, whether he’s doing anything to interfere with the probe,” Adam Schiff, the incoming chairman of the House Intelligence Committee, told NBC’s Meet the Press in an interview Sunday. “Mr. Whitaker needs to understand that he will be called to answer, and any role that he plays will be exposed to the public. We don’t want there to be any ambiguity about that.”

Investigating the acting attorney general could be a long and painful process. But Democrats can create more discomfort for Trump in the short-term, too. As Schiff told Mike Allen in an interview that aired Sunday, Democrats also plan to release the transcripts of dozens of interviews the committee has conducted as part of its own Russia inquiry, which Republicans have refused to share with Mueller. Specifically, Democrats want the public to know whether longtime Trump associate Roger Stone perjured himself when he testified, behind closed doors, regarding his contacts with Russians and WikiLeaks during the presidential election. “I want to make sure that Bob Mueller has the advantage of the evidence that we’ve been able to gather,” Schiff said. “But equally important: that Bob Mueller is in a position to determine whether people knowingly committed perjury before our committee.”

Schiff isn’t the only incoming committee chair itching to take on Trump. Congressman Jerrold Nadler, who is expected to take over the House Judiciary Committee, told CNN’s State of the Union that he, too, plans to summon Whitaker over his criticisms of the special counsel and would even be willing to subpoena him, if necessary. But for all their warnings, the fact remains that Democrats have little recourse until they assume the majority in January. In the meantime—questions about the validity of his appointment aside—Whitaker enjoys the same authority over the Russia investigation as Deputy Attorney General Rod Rosenstein, following Sessions’s recusal last year. Without help from their colleagues across the aisle, Democrats are largely powerless to protect the probe during the lame-duck Congress. Aware of this, they’ve begun pushing to attach legislation that would prevent Whitaker from interfering with the Mueller probe to a must-pass spending bill. “There’s no reason we shouldn’t add this and avoid a constitutional crisis,” Senate Minority Leader Chuck Schumer said during an interview with CNN. A few Republicans, such as retiring Arizona Senator Jeff Flake, have expressed support for the bill.

If Democrats fail to win enough G.O.P. votes, Whitaker will remain a threat to Mueller. “It is disturbing that the president chose to elevate to the attorney general’s position someone who has expressly, manifestly indicated a certain degree of antipathy toward the special counsel’s investigation,” said David Laufman, a former D.O.J. official who worked on the Trump-Russia and Hillary Clinton e-mail investigations. Still, as the congressional aide reminded me, the situation is very much in flux. “[It’s] tough to write out a prescribed ‘Here’s exactly what is going to happen day one on January 3,’” they said, “because things are going to look so much different.”

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