It’s a very long walk, inside the Robert F. Kennedy Department of Justice Building, from Rachel Brand’s fifth-floor office to Rod Rosenstein’s space on the fourth floor. But the more important gap—in relative power—between the associate attorney general and her boss, the deputy attorney general, could shorten in a hurry.

Rosenstein has become an unexpectedly pivotal figure in the Donald Trump-Russia mess. Two weeks after joining the administration, the mild-mannered career prosecutor wrote a three-page memo that the president used to justify firing F.B.I. director James Comey. After Trump, on national television, revealed the memo to be a ruse, Rosenstein responded by appointing special counsel Robert S. Mueller III. Those twists pretty much guarantee that Mueller will eventually call Rosenstein as a witness in the investigation—at which point, goes the conventional wisdom, Rosenstein will recuse himself from all things Russia-related.

But the break could come sooner. “It really depends on Rod’s exact role in the firing of Comey, and what Trump told him,” a Department of Justice insider says. Mueller will also want to know about any communications between Jeff Sessions and Rosenstein regarding the firing, and if he establishes those links through other witnesses, Rosenstein may need to step aside even before he’s scheduled to answer the special counsel’s questions himself.

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Or he could be given a shove toward recusal by a summons from the newly energized Senate Judiciary Committee. Its rival, the Senate Intelligence Committee, has been faster out of the investigatory gate, reeling in Comey and Sessions for dramatic, headline-making hearings. This has left Judiciary members from both parties grumbling. Some blame Chuck Grassley, the committee’s chairman, for dragging his feet on behalf of his fellow Republican president; others point at Dianne Feinstein, the ranking Democrat, claiming she isn’t motivated to push for Judiciary hearings because she also sits on Intelligence and therefore has gotten plenty of Russia-related camera time.

“There are lots of frustrations among members that Judiciary hasn’t been involved,” a committee insider says. ”Intel has jurisdiction over some things, like a foreign government hacking the election. But the F.B.I. and obstruction of justice? That all should be Judiciary.”

The impatience has recently surfaced in a couple of ways. Rhode Island Democrat Sheldon Whitehouse, a former federal prosecutor, has loudly speculated that he believes that Michael Flynn, Trump’s short-lived, highly compromised national security director, has already started cooperating with Russia investigators. Dick Durbin, the Illinois Democrat, has been rankled enough to publicly nudge Feinstein that Judiciary needs to “reassert our oversight function.”