Senate Republican Conference Chairman Lamar Alexander (R-Tenn.) will announce today that conference Staff Director Ryan Loskarn will be named chief of staff at the end of the month.

Loskarn, who has been on Roll Call’s Fabulous 50 list, will replace Chief of Staff Matt Sonnesyn.

Sonnesyn has worked for Alexander for the better part of a decade, including stints in the Republican Conference, Alexander’s campaign and most recently as his chief of staff.

In a statement, Alexander called Sonnesyn “one of the most talented policy advisers on Capitol Hill.”

“For ten years we have worked closely together,” Alexander added. “I will miss his counsel.”

Loskarn is one of the Senate GOP’s top strategists and aides, and he has been a fixture in the House and Senate for most of the past decade. Including working at the Republican Conference under Alexander and former Chairman Jon Kyl (Ariz.), Loskarn also did stints in the House working for Reps. Wally Herger (R-Calif.) and Marsha Blackburn (R-Tenn.), as well as the House Rules Committee.

“I am fortunate that Ryan Loskarn is willing to transfer his considerable skills from leading the Republican Conference to leading my Senate staff,” Alexander said.

Loskarn will remain in his position at the Conference until Alexander steps down early next year.