Rosenstein just appointed a new deputy to oversee Mueller's Russia probe
Ed O'Callaghan, the Justice Department's new acting Principal Associate Deputy Attorney General. Image via screengrab.

Deputy Attorney General Rod Rosenstein has picked a longtime prosecutor to help him run the Justice Department's Russia investigation.

CNN reported Tuesday that, according to a DOJ official, former white collar defense attorney-turned-prosecutor Edward O'Callaghan is now the acting Principal Associate Deputy Attorney General.

O'Callaghan's new position, which CNN noted is referred to as the "Padag" within the DOJ, carries behind-the-scenes cachet. In the role, the veteran prosecutor and counterterrorism will advise Rosenstein on all department investigations and policy.

The report noted that O'Callaghan's most recent position was as acting head of the DOJ's National Security Division. In the role, he "raised eyebrows," CNN noted, when he addressed the press to defend the Trump administration's "use of contested terrorism figures to encourage changes to immigration policies."

Rosenstein's new deputy will replace former "Padag" Robert Hur, who last month was unanimously confirmed as the U.S. Attorney for the state of Maryland.