Jeffrey Rosen was officially sworn in as deputy attorney general Wednesday, replacing Rod Rosenstein Rod RosensteinDOJ kept investigators from completing probe of Trump ties to Russia: report Five takeaways from final Senate Intel Russia report FBI officials hid copies of Russia probe documents fearing Trump interference: book MORE as the Justice Departments second-highest official.

Rosen, a former deputy secretary of Transportation who also worked in the Justice Department during the George W. Bush administration and practiced law in the private sector, was nominated in March and confirmed by the Senate last week in a 52-45 vote.

The swearing in will put Rosen at the center of an ongoing feud between the Justice Department and House Democrats seeking documents and testimony from current and former administration officials as part of their sprawling oversight probes.

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“Jeffrey Rosen is a distinguished lawyer who has served at the highest levels of government and the private sector,” Attorney General William Barr Bill BarrHarris faces pivotal moment with Supreme Court battle Hillicon Valley: DOJ proposes tech liability shield reform to Congress | Treasury sanctions individuals, groups tied to Russian malign influence activities | House Republican introduces bill to set standards for self-driving cars McCarthy threatens motion to oust Pelosi if she moves forward with impeachment MORE said in a press release. “His years of outstanding legal and management experience will make him an excellent Deputy Attorney General.”

Deputy attorney general has traditionally been a low-profile job. However, it was thrust into the spotlight after former Attorney General Jeff Sessions Jefferson (Jeff) Beauregard SessionsGOP set to release controversial Biden report Trump's policies on refugees are as simple as ABCs Ocasio-Cortez, Velázquez call for convention to decide Puerto Rico status MORE recused himself from overseeing the Justice Department’s probe into Russian interference in the 2016 presidential election, leading Rosenstein to oversee special counsel Robert Mueller Robert (Bob) MuellerCNN's Toobin warns McCabe is in 'perilous condition' with emboldened Trump CNN anchor rips Trump over Stone while evoking Clinton-Lynch tarmac meeting The Hill's 12:30 Report: New Hampshire fallout MORE’s investigation and launching him into a contentious battle between the White House and House Democrats.

Rosen’s ascension to the Justice Department’s No. 2 slot comes as Democrats demand Mueller’s full unredacted report and underlying evidence from the Justice Department and call on the agency’s watchdog to open a litany of investigations into Barr.

Senate Democrats raised concerns during his confirmation hearing about his experience before he was sworn into the tumultuous posting.

Sen. Dianne Feinstein Dianne Emiel FeinsteinFeinstein 'surprised and taken aback' by suggestion she's not up for Supreme Court fight Democrats shoot down talk of expanding Supreme Court Biden leads Trump by 12 points among Catholic voters: poll MORE (D-Calif.), the ranking member of the Senate Judiciary Committee, said she couldn't support Rosen because he would be “learning on the job” and has a “history of partisanship that risks undermining the independence that we have so badly needed.”

Rosen sought to allay such concerns about any partisan leanings, telling senators during his confirmation hearing that “if the appropriate answer is to say no to somebody, then I will say no.”