A Republican, he previously served as a member of both houses of the Texas State Legislature.
Duncan served in the Texas State Senate from the 28th district, centered about Lubbock, from 1996, when he won a special election, until his resignation in July 2014, when he was named chancellor of the Texas Tech system.
He previously served in the Texas House of Representatives from District 84 from his election in 1992 until 1996.
Duncan holds bachelor's and law degrees from Texas Tech University.
[3] In January 2025, the office of Texas House Speaker Dustin Burrows announced that Duncan would be joining his team to serve as Chief of Staff.