A fifth generation Montanan, Rehberg has been involved in public service and ranching most of his adult life. In 1977 he began working as an intern in the Montana State Senate, and two years later he joined the Washington, D.C. staff of Montana Congressman Ron Marlenee as a legislative assistant. In 1982, Rehberg returned to Montana and ranching.

Rehberg was elected then to the Montana State House of Representatives from 1985 to 1991, where he served three terms. In the legislature, he considered himself to be a fiscal conservative, and he advocated balancing the state budget without any tax increases. He was the only freshman member to serve on the House Appropriations Committee.

In July 1991, Rehberg was appointed Lieutenant Governor by Governor Stan Stephens. The following January when Stephens decided not to seek reelection, Rehberg and Racicot sought the state’s top offices.

As Lieutenant Governor, Rehberg sought to bring government back to the local level by traveling to all 56 counties every year. He chaired the Drought Advisory Committee and the Task Force credited with reforming Worker’s Compensation, the Montana Rural Development Council, and several health care initiatives.