Topping the agenda for many members of Congress is the Russian Federation investigation being undertaken by Justice Department special counsel Robert Mueller.
The Judiciary Committee will hold confirmation hearings next week for Barr, who also served as attorney general under former President George H.W. Bush.
Some observers feared that Rosenstein's departure could spell danger for the Mueller probe.
All along, Mueller's investigation has continued, but it isn't clear to anyone outside a handful of select leaders how much longer it may run or with what effect - and consequently, what kind of effect the transition from Rosenstein to Barr might have. Associates have said Barr was hesitant to take on the job unless he could choose his own deputy, according to the Wall Street Journal.
Graham said that Barr and Mueller are friends and that Barr assured him that if he's confirmed for the top Justice Department position that he would not interfere with Mueller's work. "Following the announcement of Mr. Barr's nomination, senior Department ethics officials were consulted and advised that, under the applicable rules of professional conduct, Mr. Barr's memo would present no conflict as to his duties as Attorney General".
The White House cast Rosenstein's departure as his choice. Rosenstein said the report was not accurate.
In some ways, Rosenstein's departure is unsurprising.
ABC News, citing multiple sources familiar with Rosenstein's plans, reported that he meant to leave in the coming weeks as Barr transitioned into the job. The deputy attorney general is like a chief operating officer, managing much of the department's day-to-day activities and mediating disputes between its many sprawling parts.
Maddow announced new details from Williams, who reported that Rosenstein will stay "until Mueller winds down the bulk of the investigative and courtroom work in the Russian Federation investigation". Also, Barr wrote an unsolicited memo to the Justice Department past year critiquing Mueller's investigation into whether the president had sought to obstruct justice by firing James Comey as FBI director. Rosenstein, a former United States attorney in Maryland, will have served as deputy for roughly two years by the time he leaves.
Rosenstein's job security has frequently been in doubt, as the president who appointed him constantly attacked him privately and publicly. The appointment followed the recusal of Sessions because of his work on the Trump campaign and Trump's firing of former Federal Bureau of Investigation director James Comey.
Immediately after Comey was sacked, the FBI had opened an obstruction of justice investigation into Trump. Democratic Senators Patty Murray and Patrick Leahy said it will be critical to see who is named to replace Rosenstein. At one point, the two had an angry confrontation in which each argued that the other should be recused from the Trump investigation, these people said.
Trump has criticized Rosenstein numerous times. Instead, Rosenstein talked with Trump and stayed in his job.