With Sessions out, what will happen to Rod Rosenstein?

Deputy Attorney General Rod Rosenstein always knew his portrait would someday be added to the hallway outside of his Washington office, following in the tradition of his 28 predecessors, whose photos neatly line a row of shelves.

The only question is whether the Philadelphia native will be joining them sooner rather than later.

With congressional Democrats already promising that they'd use their newly won control of the U.S. House to place President Trump under increased scrutiny, Trump responded Wednesday with a surprise announcement: Attorney General Jeff Sessions had resigned and was immediately replaced by his chief of staff, Matthew Whitaker.

Rosenstein was next in line for the top job at the Justice Department, but the fact that he was passed over was almost beside the point. Trump had taken Rosenstein's oversight of special counsel Robert Mueller's investigation into Russian meddling during the 2016 election and put it in the hands of Whitaker, who once described to CNN how a new attorney general could theoretically choke off Mueller's funding.

Where all of this leaves Rosenstein, 53, is unclear. After a previously scheduled meeting at the White House on Wednesday, Rosenstein shook hands with Sessions as he left the Justice Department and employees gave him a warm send-off.

It was just a month ago that Trump told reporters he didn't intend to fire Rosenstein, amid a flurry of reports that Rosenstein had offered to resign after the New York Times claimed that he had once discussed secretly recording the president. "I get along with him very well," Trump said at the time.

Rosenstein, who was born in Philadelphia and grew up in Montgomery County, has long occupied an awkward spot in the Trump administration.

Trump had been relentlessly critical of Sessions for recusing himself from the Mueller investigation — "I don't have an attorney general," he said in September — but Rosenstein consistently shrugged off Trump's public complaints, insisting that he wouldn't fire Mueller without good reason.

"What we do here is not about politics. People are going to comment on what we do, people are going to criticize what we do," Rosenstein, a Republican, said last year. "But it can't affect what we do. And so, we need to make sure that we don't react to everything that's said about us in the media. That's an important part of the job — the restraint."

Former colleagues have said Rosenstein was the right person for a task like monitoring the Mueller probe; during a nearly three-decade career in federal law enforcement, he developed a reputation among Republicans and Democrats as a by-the-book straight arrow, one more concerned with following rules than bowing to political rhetoric.

Leaders from both sides of the aisle expressed dismay over Wednesday's developments. Sen. Susan Collins (R., Maine) tweeted that she was "concerned [because] Rod Rosenstein will no longer be overseeing the probe," adding that Mueller "must be allowed to complete his work without interference."

U.S. Rep. Nancy Pelosi (D., Calif.), who stands to become speaker of the Democratic-controlled House, accused Trump of trying to undermine Mueller and called on Whitaker to recuse himself, given his past criticism of Mueller's investigation. Rep. Jerry Nadler (D., N.Y.), who is slated to become the chair of the Judiciary Committee, said Rosenstein should be allowed to continue to oversee the probe.

Chris Edelson, an assistant professor of government at American University's school of public affairs, said it's difficult to speculate about Rosenstein's fate.

"If a new attorney general is overseeing the probe, it might not matter," he said. "The more pressing question to me would be, 'What would the new attorney general do with Mueller?' Shut him down? Hamstring him? We don't know."

This article contains information from the Washington Post.