WASHINGTON — The Senate on Wednesday approved President Donald Trump's pick to lead the Justice Department's criminal division following a yearlong confirmation process.

Brian Benczkowski was narrowly confirmed as an assistant attorney general with a 51-48 vote. Democrats strongly opposed the nomination, partly because of his work while in private practice for a leading Russian bank. Democrats said his Russian ties could complicate special counsel Robert Mueller's ongoing investigation into Russian interference in the 2016 election and possible coordination with the Trump campaign.

Brian Benczkowski, then Republican staff director of the Senate Judiciary Committee, sits behind the committee's then ranking Republican, Sen. Jeff Sessions, R-Ala., in Washington, on June 18, 2009. Harry Hamburg / AP file

Democrats also contended that Benczkowski did not have enough experience in federal courtrooms to run the criminal division. The position is one of the most significant in the Justice Department, with the assistant attorney general having oversight of criminal cases involving public corruption, financial fraud, computer hacking, drug trafficking and other major crimes.

Benczkowski sought to downplay those concerns at his confirmation hearing last year, saying, "Being head of the criminal division in the first instance is principally a management and leadership job." He noted that he had held multiple Justice Department posts, including serving as chief of staff to former Attorney General Michael Mukasey in the Bush administration.

"One of the things that I learned in the course of those previous positions is how important it is to consult and listen to the career lawyers in the department," Benczkowski said.

Benczkowski, who also served as an aide to Jeff Sessions when he was a U.S. senator, has most recently been a partner at Kirkland & Ellis law firm and a Justice Department official.

Sessions, now attorney general, welcomed Benczkowski to the job Wednesday, praising his diverse experience.

"This will be the sixth senior position Brian has held at the Department, and we are fortunate to have someone with his breadth of experience and strong leadership skills willing to serve again. At a time like this — with surging violent crime and an unprecedented drug epidemic — this position is especially important," Sessions said in a statement.

Benczkowski attracted attention throughout the confirmation process. He told members of Congress that he had previously represented Moscow-based Alfa Bank, which drew attention last year after U.S. news media widely reported a possible server connection between the bank and the Trump Organization. The bank says it was targeted by hackers who created a fake cyber trail to suggest extensive links with businesses owned by Trump.

That experience continued to concern Democrats on Wednesday. In a floor speech just before the vote, Sen. Chris Coons, D-Del., said Benczkowski's inexperience alone should be disqualifying. But he said he is extremely concerned about his ties to Russia, which he said "could enable him to directly interfere" with Mueller's investigation.