Harsdorf, of River Hills, is resigning her northwestern Wisconsin state Senate seat on Friday and beginning the new job on Monday. Walker is expected to call a special election to fill her seat for the same date as two others for vacancies in the state Assembly.
State Rep. Adam Jarchow, of Balsam Lake, announced he will seek the seat.
The 61-year-old Harsdorf served in the Assembly from 1989 to 1999 and has been in the Senate since 2001. She is a member of the budget-writing Joint Finance Committee.