Senate Republican Conference Chairman Lamar Alexander announced Friday the appointment of a new chief of staff in his personal office.

David Morgenstern is set to leave his post as the Tennessee Republican’s top aide on Feb. 18 to enter the private sector, according to a press release. Succeeding Morgenstern will be Matt Sonnesyn, currently Alexander’s legislative director and deputy staff director for policy in his leadership office.

“David has done a first-rate job, first as legislative director and then as chief of staff. I wish him the very best in his new opportunity,” Alexander said. “I’m fortunate that two current members of my staff are able to step into new leadership positions created as a result of David’s new opportunity.”

David Cleary, Alexander’s staff director for the Senate Health, Education, Labor and Pensions Subcommittee on Children and Families, will become Alexander’s new legislative director.